Three members of staff at the Paremoremo prison required medical treatment after being assaulted by a group of prisoners yesterday afternoon.
Police were called to Auckland Prison, known widely as Paremoremo, after a report that five prisoners had attacked a small group of workers.
The Department of Corrections confirmed the attack.
"All staff were wearing stab-proof vests and were assessed by medical staff on site,'' northern regional commissioner Jeanette Burns said.
One of the staff members was taken to hospital.
The other two were taken to an accident and emergency clinic.
"None of the injuries are life-threatening,'' she said.
Police are investigating.
Burns said: "No assault or violence is tolerated in prison. Any prisoner who uses violence will be held to account.''