The Department of Corrections has conceded that an injured prisoner, who later died, was not discovered for some time after he was assaulted.
Benton Parata was assaulted in his unit at Christchurch Men's Prison on 25 March and died six days later.
The 44-year-old is reported to have been in his cell for about 40 minutes after being attacked, before prison officers found him. He was assessed at the prison's health centre before being taken to Christchurch Hospital.
Corrections southern region commissioner Ian Bourke said staff responded quickly once Mr Parata was found injured.
But he said he could not go into details of the case ahead of a Coronial Inquest and official review of the incident.
Three men appeared at Christchurch District Court yesterday charged with his murder. Steven Betham, 36, Akuhatua Tihi, 22, and 20-year-old Levi Reuben will reappear in court on 24 April.