An inmate at the Hawke's Bay Regional Prison was found dead this morning.
Acting prison director Leonie Aben said there was no evidence to suggest that any other person was involved in the man's death.
"Every death in custody is a tragedy, and our thoughts are with his family and friends. Police have been notified and will inform the man's next of kin," she said.
All deaths in custody are referred to the Coroner for investigation and determination of cause of death.
For all unnatural deaths in custody, there is also an investigation by the independent Corrections Inspectorate and deaths are advised to the Office of the Ombudsman.