An inmate has died at Otago Corrections Facility near Milton today.
OCF prison director Jack Harrison said staff found the prisoner in an unresponsive state and provided medical attention; however, he was pronounced dead at the scene.
The death has been referred to the coroner and is subject to an investigation by the prison inspectorate and police.
St John communications advisor Ian Henderson said three ambulances were sent to the prison about 4am.
A man was treated but died at the scene.
A Fire Service spokesman said firefighters from Milton were called to prison about 4am to assist someone after a ''cardiac arrest''.
Fighters assisted with the attempted resuscitation of the man, he said.
Another inmate died at the prison in November last year.