Prison director George Massingham said two prisoners were taken to hospital for assessment of their injuries, both returning to prison the same day, and two staff also sustained injuries.
"One [staff member] was assessed by onsite medical staff and returned to finish the remainder of their shift. The other received treatment for minor injuries at an off-site medical centre."
Five prisoners identified as perpetrators of the violence had been placed in directed segregation and may face criminal charges, he said.
Mr Dennehy said the fight, which he understood occurred in a 60-bed unit, was a part of the daily violence custodial staff dealt with.
"Our department staff are facing escalating violence daily. The types of prisoners we're dealing with have changed over the years and the staff response to violence is more immediate than it has ever been.
"The severity or scope of fights varies but when you get a large number of the population in an enclosed space, as prison units are, tensions rise and something that may seem minor to the everyday New Zealander becomes an issue."
He said he was pleased the Department of Corrections was working on introducing tools such as pepper spray, which he had used as a deterrent when handling violence previously in prisons.
"We're never going to eradicate violent behaviour from people with violent tendencies. We have to try to mitigate the safety of all as best we can and the department are open to whatever tools are out there."
Mr Massingham said more than 75 per cent of the prison population had convictions for violence in their offending histories, and gang prevalence and influence was a contributing factor to the rate of violence in prisons.
"Our staff work with some of New Zealand's most difficult and challenging citizens. They responded quickly and professionally to bring the situation under control, and I am very proud of their actions."
