Corrections Minister Anne Tolley says her department will investigate if officials missed any intelligence about rising tensions at Spring Hill Prison that could have indicated yesterday's riot was coming.
Ms Tolley said the chaos was expected to cost the ministry more than $1 million and had forced prison guards to put their lives at risk rescuing inmates from being burnt alive during the riot at the Waikato prison.
Investigators today examined the damaged cell blocks where 29 high security prisoners rampaged for nearly nine hours, using volleyball poles as makeshift weapons before setting buildings alight.
Groups of prisoners not involved in the riot were kept locked in their cells until 36 specialist officers raided the cell block and arrested the rampaging inmates.
"They went berserk,'' Ms Tolley said of the prisoners who have since been relocated to other jails around the country.
"They bashed through into the guards' areas, into the officers' area, then they got all the records and the files and burnt all those.''
Ms Tolley said there were "always tensions'' among high-security prisoners but she didn't believe there was any intelligence to indicate a riot was imminent.
"I'm very confident that what intelligence they had was accurate,'' she said.
"The Corrections inspector will go over the whole thing from start to finish. We're always trying to learn what we can do better.
"I'm very confident that the intelligence that they had didn't show any extra tension or any inter-gang rivalry.''
Last night she blamed the violence on notorious gang the Killer Beez, saying the riot "is all to do with politics within the gangs''.
"Thirty per cent of our prisoners are gang members so there's always tension. They tell me the intelligence doesn't show anything out of the ordinary leading up to this.''
Three Corrections officers and two prisoners were injured during the rioting.
Ms Tolley said the guards' building destroyed by fired would cost "hundreds of thousands of dollars, up into the early millions'' to replace.
The rioting inmates were expected to face multiple charges, including for arson and assault.
Corrections chief executive Ray Smith said many of the prisoners involved had "long histories of violence and unpredictable behaviour''.
"No matter what the prisoners' motivation was, their behaviour is unacceptable and will not be tolerated,'' he said.
"They will now face the consequences of their actions.''