The standoff on the roof at Hawke's Bay Regional Prison has ended after the last four youth inmates surrendered to authorities.

The capitulation came at 1pm, just under an hour after a second inmate protesting on the Youth Unit roof had agreed to come down.

Corrections chief custodial officer Neil Beales said the inmates had been "safely removed" from the roof.

"Staff did an excellent job calmly de-escalating the incident and I would like to acknowledge them for their professionalism and bravery," he said.

"The incident was resolved without injury and without risk to the safety of the public or the wider security of the prison."

A full review of the protest would now be carried out and the matter would be referred to police, Beales said.

"Early indications are that the prisoners were upset because they weren't allowed to go into the unit's sports area yesterday but the reasons for the incident will be the subject of the review.

"There has been damage to the unit, including broken windows. A full assessment will be carried out to determine the extent of the damage."

Prison guards take the youth inmates back into custody after the group surrendered. Photo / Warren Buckland

Riot squad members had earlier gathered near the roof as five inmates hurled debris off the building.

Corrections said at 12.40pm that an inmate had come down. Earlier this morning one of the original group of six had surrendered.

Four inmates remain on the roof of the prison.

Some can be seen throwing lengths of wood and other material off the roof towards those below them, including riot squad members with shields and firefighters.

Corrections Minister Kelvin Davis reiterated that he had the "utmost faith" in the Corrections officers responding to the stand-off.

"The professionals who are trained to deal with this sort of situation are dealing with it," he said.

Davis said how the group got up to the roof will be looked into.

Davis said he had no concerns about the treatment of youth inmates at the facility.

"Corrections does a fantastic job of trying to meet the needs of people who are in prison and I'd hate to speculate on the reasons why they've decided to do this," he said.

Six prisoners, aged 17-19, accessed the Youth Unit roof yesterday afternoon.

Prison riot squad members can be seen massing near the roof. Photo / Warren Buckland

The five inmates on top of the prison roof hurl objects including wood. Photo / Warren Buckland

A prisoner negotiation team had been "engaging" with the inmates throughout the night, Corrections chief custodial officer Neil Beales said today.

"We are taking all appropriate steps to ensure the prisoners' safety and bring the incident to an end."

Five inmates remain on the roof of the Youth Unit today. Photo / Warren Buckland

The area is within the secure perimeter of the prison's unit and Beales said there was no threat to the wider security of the prison and no threat to public safety.

All other inmates in the Youth Unit were safely secured.