The Corrections Association says the police have been investigating possible corruption at Rimutaka Prison for the past eight weeks.
Rimutaka Prison (file photo) Photo: RNZ / Richard Tindiller
In early August police confirmed to RNZ there was an ongoing investigation into what it said were 'matters' at the prison.
RNZ understands the investigation relates to gang members, money laundering and inmates paying Corrections staff.
Police said the investigation, being run by the National Organised Crime Group had been running since July, prompted by information gathered in an earlier police operation.
Corrections Association president Alan Whitley said more than 70 officers have been involved in the investigation.
"All we've heard is that the investigation is into possible corruption," he said.
"We've been aware that the police have been doing an investigation there for quite some time.
"We don't know all the details of it, but it's been running for probably six to eight weeks now."
He said not everyone who had been interviewed as part of the investigation would be suspects, but could be witnesses or just gathering information.
Whitley said if there had been any kind of criminal activity they will expect to see charges soon.
The investigation is a good thing, he said.
"If there is something there, it needs to be found and rooted out, there is no tolerance for that in our line of work."
Detective Inspector Stuart Mills, the investigations manager with the National Organised Crime Group, said the vast majority of the staff who had been interviewed had been co-operative.
"The investigation remains ongoing and no charges have been laid at this stage."
Mills said for operational reasons the police were unable to confirm the nature of the investigation.
Minister of Corrections Kelvin Davis said the enquiries relate to alleged offending that began some years ago.
"My very clear expectation is that Corrections staff conduct themselves with the utmost professionalism and integrity.
"There is absolutely no tolerance for conduct that undermines the integrity of the prison system," Davis said.
A report from 2017 found Corrections staff at Rimutaka were overly familiar with inmates and did not show enough discipline with them.
The Department of Corrections said staff from Rimutaka prison were assisting police with enquiries underway at the site.
In a statement the department said it welcomed the enquiries being undertaken by police.
"The overwhelming majority of our people act with integrity, honesty and professionalism, and those who don't place their colleagues' safety at risk, damage trust in their profession and undermine the integrity of the prison system.
"They inevitably get found out, and held to account for their actions."