An expert on prison violence says it's often sparked when something prisoners are promised later doesn't happen.
Six teenage prisoners ended their 24-hour protest on the roof of Hawke's Bay Regional Prison early yesterday afternoon.
A review is underway, but the Corrections Department's chief custodial officer Neil Beales told RNZ it may have been sparked by the withdrawal of access to a sports area.
Clinical psychologist Dr Armon Tamatea, who's running a project on understanding and reducing prison violence, says having requests fulfilled is a big deal for prisoners.
He spoke to Guyon Espiner.
