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Complaints by four women are still being dealt with and legally assessed by Operation Austin, the investigation into police sexual offending in the Bay of Plenty in the 1980s.
Operation head Detective Superintendent Nick Perry told the Herald the complaints were not "full-scale" complaints like that by Louise Nicholas.
"They are mainly related to earlier police procedures where they were not dealt with properly," he said from London today.
Mr Perry would not comment on what current or former officers the complaints related to.
He said legal opinions were being sought, and could not say if charges could result.
Mr Perry said he was pleased the professionalism of the Operation and his staff were recognised by the Independent Police Conduct Authority review released yesterday.
The review revealed the scale of Operation Austin for the first time, saying it examined complaints concerning 50 women.
Twenty-five were regarded as hearsay or insupportable but the other 25 warranted serious investigation by police.
The IPCA yesterday dismissed claims that Operation Austin was flawed.
The authority instead hailed it as an exceptional major criminal investigation conducted at a level of excellence several grades above what would normally be expected.
And it dismissed 15 complaints about it by former assistant commissioner Clint Rickards.
In March, Mr Rickards said Operation Austin was a shambles he would have been ashamed to lead.
But the complaints authority said it had been an excellent investigation with aspects that should become standard police practice.
Operation Austin began in 2004 after Louise Nicholas alleged she had been raped in the 1980s by Mr Rickards and now-jailed former officers Brad Shipton and Bob Schollum.
Last year the trio were acquitted of sex charges against Mrs Nicholas, and in March they were acquitted by a jury on charges of kidnapping and indecently assaulting a then-16-year-old girl more than 20 years ago.
It was after this second trial that Mr Rickards made his attack on Operation Austin.
Shipton and Schollum are in prison for raping a Mt Maunganui woman 18 years ago.
In August, former Rotorua CIB chief John Dewar was found guilty of obstructing the course of justice for his handling of allegations made by Mrs Nicholas.
Complaints authority investigators contacted 50 women who had complained to Operation Austin or had been contacted by its staff, to assess how well officers had dealt with their complaints.
"The inquiry was almost overwhelmed by new matters virtually every week," the authority report said.
"New allegations were reported on a regular basis and many of these had remarkable similarities to the Nicholas case.
"The investigation by its very nature needed to be, and was, thorough."
Operation Austin investigated the complaints of 25 victims in detail. The authority said the management of each of those case files set new standards for police investigations, and the victim management policies - which included assigning each complainant a victim liaison officer and giving assistance from Victim Support - was groundbreaking.
"It is yet another example of the operation having left no stone unturned in its efforts to rectify the damage to the victims and to the police's reputation by a few rogue elements within their ranks."
The complaints authority recommended that many of Operation Austin's methods should become part of the police manual of best practice.
"The victims who came through Operation Austin have been thoroughly and professionally dealt with." the report said.
"Nonetheless, further complainants may surface at some time in the future for a variety of reasons."
Yesterday, Louise Nicholas said she was pleased the work of the police who investigated her case had been given such high praise.
"At the beginning I was a bit sceptical about the investigation but over the months as it unfolded, I had nothing but high praise for the way they treated me and my family," Mrs Nicholas said.
"It was my husband Ross who said, 'Here is your opportunity'.
"I was worried they were going to brush it under the carpet, but Ross said, 'Give these guys a go but if you smell any rat we will blow it open'.
"But it didn't end up like that," Mrs Nicholas said. "I gave them the opportunity and they proved me wrong, which was cool."
OPERATION AUSTIN
* Operation Austin was the investigation allegations of pack-rape and corruption by police. It began in 2004 after allegations by Louise Nicholas were made public.
* The investigation was headed by Detective Superintendent Nick Perry who is now the police liaison officer at the New Zealand High Commission in London.
Mr Rickards has been scathing about the police team set up after the Nicholas' allegations surfaced, and filed 15 complaints with the Police Complaints Authority.
* Mr Rickards and former police colleagues Bob Schollum and Brad Shipton were found not guilty in March of kidnapping and indecently assaulting Mrs Nicholas in Rotorua more than 20 years ago.
* Mrs Nicholas has described Operation Austin as having restored her faith in the police force.
