An ongoing riot at Waikeria Prison has destroyed a third of its bed capacity with no end in sight.
Seventeen prisoners remain non-compliant after four gave up overnight. Negotiators are working to defuse the situation which has be ongoing for more than 24 hours.
Rioting prisoners lit several fires in an exercise yard and many are still smoldering, Department of Corrections chief executive Jeremy Lightfoot says.
Prisoners have climbed onto a roof and are continuing to cause mayhem.
The exercise yard has shower doors, which may have been used as weapons, Lightfoot says.
Corrections do not know what triggered the riots but it's understood a lack of access to phones could be the cause.
No food has been supplied to the prisoners on the roof since they began the riot.
Police negotiators are working alongside Corrections but Lightfoot would not go into details about how they were communicating with the prisoners.
The rioting is the biggest in a New Zealand prison since 2013 when more than 20 prisoners went on a rampage at Springhill Prison.
The inmates destroyed property during the nine-hour siege, smiling and waving to cameras as they set two cell blocks on fire.
They also smashed cells with makeshift weapons. Three Corrections officers and two prisoners were injured.
About 100 prisoners had to be moved to other prisons during the Spring Hill riot.
Corrections were contacted by media about midday yesterday after receiving a tip that a riot was planned.
A spokeswoman says they acted immediately to carry out checks and everything was quiet. It was afterwards when prisoners were in the exercise yard that they started to light fires.
Lightfoot says he would not be sending any of his staff into the unsafe environment, saying "we must be focused on the threat to life".
Damage to the top jail has been "significant" and it is unlikely prisoners will be able to be accommodated there again.
Lightfoot said the prison is losing roughly a third of the prison's capacity - 250 beds - as a result of the fire damage.
About 45 Fire and Emergency New Zealand staff are on scene. At the height of the blaze, there were 75.
There were concerns about smoke inhalation for prison staff but no one was treated for any injuries, Lightfoot says.
The most important stage of the riot response was removing prisoners not involved and staff safely away.
Prison Corrections Association union rep Alan Whitley said the section of the prison is far beyond its use-by date.
One of the prisoner staff managers said guards work in "horrible" conditions in that older section of the facility.
Whitley said guards works in "horrible" conditions in that older section of the facility and are "pretty nervy" working there today.