Three staff have been attacked by a group of five inmates at Paremoremo prison in Auckland.
Corrections said all three of the guards were wearing stab-proof vests, but would not confirm the assault was a stabbing.
None of the injuries were life threatening.
However, one officer was taken to hospital for treatment, with the other two taken to a local accident and emergency clinic yesterday afternoon.
The police are investigating.
Northern Regional commissioner Jeanette Burns said no assault or violence was tolerated in prison and prisoners would be held to account.
