The Herald approached Child, Youth and Family for comment on Wednesday.
Today, CYF's regional director Sharon Thom said contact with the family began while the grandmother was also living in the household.
"Unaware she had moved out, it is now clear the situation for the children swiftly changed."
The written statement from CYF did not address whether checks were performed on the children and why the abuse wasn't uncovered sooner.
"This case demonstrates the length some parents will go to conceal the abuse of their children. The result is the children's home being turned into a place of pain and fear," Thom said.
The agency was "deeply appreciative" of the school making a Report of Concern and referred the children to a specialist unit of child trauma professionals "to help the children to overcome what they have suffered".
The siblings were now in the care of their wider family.
"The abuse suffered by these children at the hands of the very people meant to love and protect them is abhorrent," Thom said.
10 MONTHS OF ABUSE
At the caregivers' sentencing yesterday, the court heard how the door handles were removed from the children's bedrooms so they couldn't leave by themselves.
They were forced to spend long periods of time locked up alone while their caregivers smoked weed and meth or watched movies downstairs.
Going without food was a common punishment. If the children misbehaved, they would miss out on dinner, and sometimes breakfast as well.
They were always so hungry, teachers at the three eldest children's school would make them sandwiches and give them fruit daily.
But if Kataina found out the children had eaten when they told her they hadn't, she hit them repeatedly and denied them dinner, breakfast or both.
As well as being starved and neglected, the children were beaten repeatedly on a weekly or sometimes daily basis, with the defendants' hands, or with weapons like spoons or other utensils.
The eldest children bore the brunt of the beatings.
Kataina once lost her temper with the 6-year-old and slammed the girl's head into a wall at least twice, leaving a hole.
The father shoved the 8-year-old's head into the wall and floor of a bedroom about 20 times, as well as hitting it numerous times.
Kataina often lost her temper with the 3-year-old, once because he'd used Dax Wax gel in his hair, so she grabbed him by the ears and pulled him up to her neck level.
She threatened to hang him from the clothesline by his ears, and once both caregivers taped him to it by his arms and hands.
"When the child victims were hit by the defendants ... they were never hit just once, they would be hit repeatedly and hard, sometimes for minutes at a time," the court documents said.
Kataina was identified as the "main abuser", hitting the children regularly and yelling encouragement to her partner when he hit them, telling him to hit them harder.
Some of the beatings were because the children climbed a tree and broken a branch, gone down the road with a family friend, denied eating food, or got a sibling a paracetamol.
As a result all the children had bruising and red marks on their bodies, with the eldest two also suffering black eyes, scratches and dizziness.
After teachers reported the injuries on October 29, 2014, the man admitted disciplining the children by smacking their hands or kicking them in the bum. Kataina denied assaulting any of the children.
They continued to deny the charges until the day of trial last year when they finally admitted their offending after negotiations with the Crown.
Judge Gregory Hikaka said Kataina had shown a "gross abuse of trust", with the abuse beginning just a week after she started a relationship with the children's father.
An aggravating feature was the "cruelty" of the abuse, in particular taping one of the boys to the clothesline, as well as the violence, the use of weapons, abuse of trust and the extent of harm, the judge said.
The children were now showing signs of being violent towards each other, which was a "typical example of the continuation of the cycle of abuse".
Kataina was jailed for two and a half years and the father was sentenced to 23 months, which could be transferred to an electronically monitored sentence once a suitable address was found.
