The Department of Corrections has confirmed a serious assault on a prisoner at Hawke's Bay prison.
Hawke's Bay Regional Prison manager George Massingham said a prisoner was seriously attacked by other prisoners on Saturday.
The man is in hospital in a critical condition.
Mr Massingham said the police were investigating, and he expected charges would be laid in relation to the attack.
He said the Department of Corrections had a zero tolerance policy toward prisoner assaults on staff and other prisoners.
But he said assaults do happen from time to time.