An Auckland Prison staff member was injured in what the Corrections Department says was an unprovoked attack by three inmates using makeshift weapons.
Corrections said the staff member had to be taken to hospital after the incident yesterday, but has since been discharged.
Prison director Andy Langley said the three inmates involved in the attack were also taken to hospital.
Two were treated and returned to the jail .
The police are now investigating.
The president of the Corrections Association Alan Whitley said the high number of assaults on staff at Auckland Prison was concerning, and he wants to see harsher penalties for any prisoner that assaults a staff member.
Mr Whitley said pepper spray, which will be available to staff at Auckland Prison from July, will reduce the number of staff hurt in such attacks.