The Weekend Herald has revealed today that police are now reinvestigating the disappearance of Peter Boland, 9, who went missing in August 1957.
It is one of the oldest known cold cases of missing children in New Zealand.
But there have been a handful since.
While thousands of people have gone missing over the years, the majority are found. We have taken a look at the cases where the child or teenager has never turned up.
READ MORE
• Police investigate 60-year old case of missing child
• Missing without a trace: Police never investigated boy's disappearance
• TV's Sensing Murder: The search for a missing boy
• The case of Amber-Lee
On September 15, 1961, the Lower Hutt typist disappeared after meeting with John Maltby, 30, for an interview as a calendar model.
Maltby had placed an ad in a newspaper under a fake name.
Police told the Weekend Herald the Mayes case is considered New Zealand's "oldest missing person case on record that became a homicide investigation".
She was last seen getting into his car in Manners St after answering the newspaper advertisement.
Her boyfriend Kenn Morrissey was arrested and interrogated for three days, before being released by police, who accepted that he was at sea when she vanished.
Nine days after Mayes' disappearance, Maltby's body washed ashore at Island Bay.
Her body has never been found.
A Wellington coroner ruled in 2008 - 47 years after her disappearance - that she was the victim of foul play but there was not enough evidence to say who had murdered her.
The Morrinsville toddler was last seen in 1964.
Despite more than 52 years of investigations, authorities haven't been able to shed any light on what happened to Betty.
She was the daughter of farm workers Charlie and Marion Wharton, who were considered suspects in her disappearance for many years.
They were both sent to prison after the death of Betty's older sister, convicted with failing to provide the necessaries of life.
When Betty was born the couple were being monitored by authorities, but because they moved around a lot for work they fell through the cracks.
And when child welfare workers eventually located the Whartons, Betty was no longer with them.
The couple told police Betty was in the care of her grandfather, but later changed their story to say she had been informally adopted by a Te Awamutu woman named Martha.
The couple have since died.
Police in 2017 were preparing to officially close the case and refer Betty's disappearance to the coroner.
The 2-year-old went missing in Tokoroa in September 1968.
He had gone outside to play in the neighbour's sandbox with his friend, 2-year-old Karen Stubbs.
She told her mother Colleen Stubbs and Jefferie's older brother Robert Hill, 6, who was playing on his tricycle, that Jefferie had fallen into the Matarawa Creek.
Despite an extensive search of the creek, Jefferie's body was never found.
In August, nearly 50 years on, Jeffrie's mother Jo Reynolds told the Herald on Sunday she didn't know what to believe.
The teenager vanished while hitch-hiking from Hamilton to Hastings on Queen's Birthday weekend in 1975.
Detective Inspector Mark Loper from Rotorua led the team of police which found officers working on the case possibly put too much weight on a truck driver's evidence that he saw Blades get into an orange Datsun on the Napier-Taupo Rd with a man.
Her disappearance sparked one of the country's largest manhunts with more than 500 suspects who either owned or had driven orange Datsuns investigated.
However, not one piece of evidence or her body was ever found.
A new documentary released last year revealed the truck driver's evidence changed slightly each time he was interviewed by police, meaning he was possibly influenced by what he had heard and read of the case.
That meant the inquiry team possibly didn't put enough weight on other apparent sightings of Blades in the Taupo area, particularly from those who said they saw her drinking at the Spa Hotel in Taupo with another young woman.
Loper said in the documentary he now did not think Blades left Taupo alive.
Detectives said they discovered Blades had some affiliations with bike gangs in Auckland and Hamilton and it was possible that those gangs were on the road travelling to Wellington for a gathering over that long weekend.
The documentary revealed there were also sightings of a red Toyota station wagon that could have been travelling with a bike gang that corroborated with another witness who saw two people carrying a rolled up piece of carpet into the back of a red Toyota station wagon in Taupo.
The Napier schoolgirl disappeared on September 1, 1983, while on an after-school ride with horse Commodore.
The alarm was raised after she failed to return home as expected about 5pm. Her mother Robyn Jensen called police about 5.45pm.
Concerns escalated when the horse was found tethered near an old World War II gun emplacement on the Napier side of the Tutaekuri River mouth, but there was no trace of the girl, a pupil at Colenso High School (now William Colenso College).
Amid nationwide publicity, and an offer from Napier newspaper the Daily Telegraph to post a $5000 reward, information came from several people based on what they'd seen in the area.
Among these was Whakatu orchard worker John Russell, who initially told of driving past and seeing a girl talking to man, holding her at arm's length and near a parked white truck.
Much publicity focused on further information about the truck, and police spent some time focusing on Russell, establishing that his movements appeared to be legitimate and suitable for an alibi.
During the process, Russell was to tell police he was that man to whom he had referred, and that he had been driving past when he saw a girl with a horse and turned back to see if she was alright. He said the girl had blood on her face and told him she had fallen from the horse and someone had gone to contact her parents.
Police searches of his vehicle and home did not find anything to suggest Kirsa had been there, but police did establish a piece of rope used to tether Commodore matched rope from an awning Russell had been getting rid of on behalf of his employers.
The case took a bizarre twist when Russell made a confession in 1985.
At one stage he drove to TV studio Avalon in the Hutt Valley, wishing to confess and crashed on the way back to Hawke's Bay.
He later retracted the confession and told interviewer Paul Holmes he had been mentally ill.
Apparently tormented by his association with the events or the inquiry, he spent time in psychiatric institutions and took his own life in 1992, when he was found dead in a Hastings boarding house.
Ian Holyoake, head of the Napier CIB at the time of the disappearance, ttold Hawke's Bay Today in September he remains open-minded on whether Russell was their man, and does wonder how much the "stupid bloody white truck", which probably didn't exist, may have interfered with people's recollection or views on what they may have seen to the extent there may still be crucial evidence that was never reported to the police.
Joanne went missing in Auckland Central on November 19, 1988.
She was last seen prior to midnight leaving a function at Auckland University Campus and walking down Princes St towards Wellesley St.
Detective Senior Sergeant Shaun Vickers has said Joanne was likely the victim of foul play and despite the case remaining unsolved, police are determined to leave no stone unturned in an effort to confirm Joanne's fate and finally bring closure to her family.
In December, police offered a $50,000 reward for information which leads to the identity and conviction of any person or persons responsible for any criminal offence committed against Joanne.
A similar reward was offered in this case in 2007, but unfortunately no information came forward that was able to help the investigation and the reward was unclaimed.
In 1992, the 2-and-a-half-year-old vanished at Kingston near the southern end of Lake Wakatipu.
Despite exhaustive searches, there has never been any sign of her.
Retired detective Warwick Walker and the current officer in charge of the case believe Amber-Lee was taken, killed and her body disposed of.
"The most likelihood is that somebody has taken her, somebody is involved and there is somebody out there who knows that," Walker said.
In 2017, the Herald launched Chasing Ghosts, a six-part podcast series, news feature and mini-documentary about Amber-Lee's disappearance and the aftermath.
It marked the 25-year anniversary of the toddler going missing.
There are thousands more missing children cases around the world. These are some of the most high profile.
The trio never returned after leaving their parents' home in Glenelg in Adelaide for an afternoon at the beach on Australia Day, 1966.
Their disappearance sparked a wide-scale search operation, but Jane, 9, Arnna, 7, and Grant, 4, were never found.
Sightings of the children at Glenelg on the day they disappeared put them in the company of a tall, blond and thin-faced man with a suntan.
Their disappearance sparked a string of enormous investigations and saw detectives "inundated" with people trying to help find them.
In 2013, new information focused the investigation on a factory west of Adelaide, after two brothers told police they spent the 1966 Australia Day weekend digging a large hole there at the request of owner Harry Phipps.
Phipps died in 2004, but his son, who accused his father of years of sexual abuse, believed he had a part in the crime.
He also bore a resemblance to an identikit picture prepared at the time, and lived close to Glenelg Beach.
An initial excavation at the North Plympton site proved fruitless, but police said last year they believed they had been digging in the wrong spot.
But the dig was called off after they found only animal bones.
In late 2016, South Australian police identified a 71-year-old former Adelaide scout leader as a person of interest in the mystery.
Millionaire bar owner and convicted paedophile Anthony Munro is in jail for unrelated child sex offences in South Australia dating back to 1962 — four years before the Beaumonts vanished.
Police interviewed Munro in June 2016 about Australia's greatest child abduction mystery after a child's diary said he was at Glenelg beach in the days surrounding the Beaumont children's disappearance.
The "salvage and exploration club" diary was kept by one boy, and contributed to by another, tracking their adventures diving off the Adelaide coast that summer.
Police have previously said there is no evidence linking Munro to the disappearance of the Beaumont children.
Another man who was linked to their deaths, Munro's friend Allan "Max" McIntyre, died in a nursing home on the Yorke Peninsula west of Adelaide June last year, aged in his late 80s.
His son, Andrew McIntyre, who was sexually abused by Munro, broke his silence last year revealing his father and Munro were frequenting Glenelg beach in the days around the disappearance of the three children.
Detective Stanley Swaine, who died in 2002, was widely discredited following his retirement from the South Australian police force, but his obsession with the case continued well into his second career as a private investigator.
Swaine led the case from 1967 when the Beaumont parents believed their children could still be alive.
He notoriously made an abortive trip with Jim Beaumont to Melbourne to investigate letters written by a person who claimed to know where the children were and that they were well-looked after.
In 1996, after the 30th anniversary of the children's disappearance, Swaine made the outrageous claim that he had found a 40-year-old Canberra woman who was Jane Beaumont.
He said all three Beaumont children had been taken and raised by a satanic cult.
Weeks before he died, Swaine made another claim about the Beaumont children to a journalist, saying he knew where they were buried and that a priest had told him it was in a church cemetery in Adelaide.
- news.com.au
The little girl went missing on the evening of May 3, 2007, from a ground-floor apartment in a complex in Praia da Luz, Portugal, where she was sleeping with her two-year-old twin siblings.
McCann's parents Gerry and Kate claim their daughter was abducted through a window while they dined with friends in a restaurant 55 metres away.
The family were on holiday from the UK.
The parents checked on the children throughout the evening, until Madeleine's mother discovered she was missing at 10pm.
The McCanns were initially given arguido (suspect) status in September 2007, which was lifted when Portugal's attorney general archived the case in July 2008 because of a lack of evidence.
The parents continued the investigation using private detectives until Scotland Yard opened its own inquiry, Operation Grange in 2011.
The senior investigating officer announced that he was treating the disappearance as "a criminal act by a stranger", most likely a planned abduction or burglary gone wrong.
In 2013, Scotland Yard released e-fit images of men they wanted to trace, including one of a man seen carrying a child toward the beach that night. Shortly afterwards, the Portuguese police reopened their inquiry.
More than £11million has been spent on Operation Grange while the Home Office confirmed it is considering an application from police for more money.
This week, the former superintendent at Nottinghamshire Police, Retired Superintendent Peter MacLeod, broke his silence in an explosive podcast saying it was "not possible" for her to be kidnapped using the window as an escape route.
MacLeod, who had visited the apartment complex and inspected Maddie's ground floor bedroom, produced specific details of McCann's room saying it discredits the family's theory of what happened.
"The window is only absolute maximum 50cm wide, in reality about 46cm wide, and it's already a metre off the ground," he said on the podcast titled Maddie.
"I had a [inaudible] at that and my shoulders are wider than that little window. So although you could climb in sideways you certainly can't jump in if you are a normal-sized person.
"But of course the shutters are the problem, because the shutters are going to be bashing down on your head. Either that or you've got to put a piece of wood in or something. And there's no suggestion of any of that.
"Then you've got to pick up a child without waking it up, without waking the other two children. I do not think it can be done, or let me put it another way, I do not see how anyone could do it.
"I frankly do not think it's possible."
William's disappeared from his foster grandmother's home in 2014 at Kendall, on the NSW mid North Coast.
He was wearing his Spiderman costume at the time.
The abduction sparked one of the biggest manhunts in Australian history but no trace of the missing boy has ever been found.
Police say William began a game, running around the back of the house underneath the balcony to hide.
By 10.30am William's foster mother realised William was missing; neighbours helped in a search for him.
At 11am, she called the police.
A directions hearing was held in December which declared it wasn't possible to conclude that missing NSW boy William Tyrrell is dead based on the current evidence.
An inquest is set to be held in Sydney this month.
Washing machine repairman Bill Spedding has previously been named as a person of interest, but has always denied any wrongdoing.
Another person of interest, Tony Jones, was questioned by police but has also denied any involvement.
Several other persons of interest, who have never been publicly named, may be called at the inquest to reveal what they know, as well as other witnesses who the Coroner considers may have evidence relevant to the investigation.
It's understood a NZDF aircraft and multiple helicopters are involved.