Six inmates at Hawke's Bay Regional Prison have come down from the youth unit's roof after spending the night there.
The prisoners, aged between 17 and 19, were on top of the youth unit since Monday afternoon.
Two of the prisoners came down this morning and the remaining four after noon Tuesday.
A fire sprinkler had been set off by prisoners inside the unit this morning, a Corrections spokesperson said.
Specialist teams were called to the prison last night to negotiate with the group.
A full review will be carried out and the matter will be referred to police.
Corrections said early indications were that the prisoners were upset because they were not allowed to go into the unit's sports area yesterday but the reasons for the incident would be the subject of the review.
Corrections said a full assessment would also be carried out to determine the extent of the damage to the unit but there were broken windows.