A prisoner from Auckland Prison at Paremoremo has been taken to hospital with serious injuries.
Corrections said the man was injured during a suspected assault at the prison this afternoon.
The department is refusing to name the injured man but Radio New Zealand understands he is Nikki Roper, who is serving a life sentence for murdering his former girlfriend, Alexsis Tovizi, in 2010.
Northern Regional Commissioner for Corrections, Jeanette Burns, said the police are investigating the incident.
Radio New Zealand understands an incident occurred between in D block - the maximum security wing of the prison.