An inmate has died at Ngawha prison in the Far North.
The Corrections Department says staff gave medical assistance but were unable to revive the man who was pronounced dead by ambulance staff.
The death is not being treated as suspicious.
A department spokesperson says a review will now be undertaken by the Independent Corrections Inspectorate - standard procedure for all deaths in custody.
Police say they were notified of the death about 1.30am on Sunday.
