A man is fighting for his life after an incident at Auckland Prison at Paremoremo this afternoon.
The incident is understood to be a stabbing.
The man is at Auckland City Hospital in a critical condition.
Corrections spokeswoman Jeanette Burns confirmed an incident involving two prisoners occurred. She said one person was treated on site and had been taken to hospital.
Police have been notified and are investigating.
"Corrections takes the issue of violence extremely seriously and staff and public safety is our top priority," said Burns.
"Corrections manages some of New Zealand's most difficult and challenging citizens, violence is always a risk as many offenders resort to violent behaviour as a means of resolving issues and of expressing themselves. Prisoners can be volatile and unpredictable and many have long histories of antisocial behaviour."
"Corrections will not tolerate prisoners using violence against staff or other prisoners, and when this does occur the prisoner/s involved will be held to account for their actions."
It is understood a man is in critical condition.
Police were called to the prison at 2.44 this afternoon.
Kahn Cawte, 29, was heading out the door to go to Snowplanet when he saw two unmarked police cars zoom past about 3.15pm.
"They had their sirens on. They were in a hurry; I thought something must have been up."