The Rimutaka probe indicates some jailers are breaking their code of conduct.
Possible mismanagement and unprofessional conduct - rather than corruption - have been the main findings of the independent inquiry into Rimutaka Prison, the head of the inquiry says.
But barrister David Patten said yesterday the problems at the prison were the result of the actions of a few.
"It would appear that there is a very small group of people that are breaching, quite fundamentally, the officers' code of conduct," he said.
"At this stage I have not reached a conclusion as to whether there is corruption. Mismanagement perhaps, inappropriate behaviour perhaps, but those issues are a long way from corruption in the sense [of] officers on the take."
The inquiry has so far pointed to four out of the 11 suspended officers at Rimutaka; the other suspensions were made independently of the inquiry.
Corrections chief executive Barry Matthews has said the inquiry was certain to snare more officers, but could not say how many.
The investigation has also led to regional manager Dave East being placed on special leave. He is facing claims of mismanagement - not corruption - and will learn today if he is to be suspended.
Mr Patten said several matters were being evaluated. "[With] some of the matters, we have been satisfied that proper procedures and processes were followed."
He and a former police officer have conducted about 60 interviews with inmates, staff and former staff since November.
"Every week and every interview, suggestions are being made to follow new lines of inquiry. There are two areas we wish to pursue as a result of interviews [yesterday]." He said the relationship between acting prison manager Chris Smith and crime prevention officer Rachel Sayers had come up in interviews, but no one had directly said it deterred them from exposing corruption.
