An inmate at Christchurch Men's Prison has been taken to hospital with serious injuries after a reported assault.
Canterbury police are investigating the incident, which happened at the prison in at about 9.30am today.
The victim was taken from the prison in Templeton, west of the city centre, to Christchurch Hospital and police investigations are continuing.
Corrections Department Regional Commissioner (Southern) Ian Bourke said the prisoner's injuries were being treated in hospital but no update on his condition was available.
Mr Bourke said prisons managed some of the country's most difficult citizens and violence was always a risk.
He said the Corrections Department would not tolerate violence against staff or other inmates and said, when this did happen, those involved would be held accountable.