Rioting at Waikato's Waikeria Prison is entering a third day after prisoners started setting fires on Tuesday, forcing the facility into lockdown.
A standoff between inmates and negotiators is continuing. Negotiators on Wednesday were withholding food and water in a bid to starve out the remaining 17 prisoners.
A Corrections spokesperson told Newshub on Thursday there had been no change to the situation overnight.
During a press conference on Wednesday afternoon, Corrections admitted they had no idea the riot was about to erupt until Newshub alerted them to a tipoff.
"Yesterday at about midday we received a call from Newshub to advise that they had received a call alerting them to a potential riot," Corrections chief executive Jeremy Lightfoot said.
After lighting small fires in an exercise yard and ripping off shower doors to fight guards, around 20 prisoners made it onto the roof of the old jail.
The mattresses they set alight lit up the valley and were visible up to 10km away.
"I could hear the sirens and people yelling," eyewitness Corli Ryan said. "I could hear the crackling of the fire and popping."
Corrections said over 200 inmates had to be moved away from the burning unit to safety. So far, only four of the 21 responsible have surrendered, Lightfoot said.
"We are clear about the criminal wanton damage that these individuals have undertaken on property and exposed so many people to potential loss of life."
Up to 70 firefighters, multiple ambulances and specialist advance control and restraint teams have been dispatched from all over the North Island since the riot began.
Callers from within the jail told Newshub conditions in it are inhumane, a sentiment shared by the very guards they're clashing with. Corrections Association president Alan Whitley admitted: "It's beyond its use by date."
The 750-bed capacity jail was built in 1911 and is now beyond repair with a third of the cells destroyed in the fire.
"Damage to the top jail facility does appear to be significant," Lightfoot said.
"The condition of the buildings will certainly need to be assessed but it is unlikely prisoners will be accommodated there again."
On Wednesday, the 17 prisoners holed up in the top jail told Newshub they're calling family members to say goodbye.
Corrections won't divulge its plan to end the ordeal but hinted starving them out is one option.
"We have not been providing them with any additional food and water," Lightfoot said.