A man died yesterday while in custody at Tongariro Prison after a suspected medical event.
Megan Tuhoro, the prison's director, said her staff made every effort to save him.
"Our thoughts are with the man's family and friends."
Other men in the unit and staff were being provided with support, Tuhoro said.
She said there was no indication his death was suspicious.
"All deaths in custody are referred to the coroner for investigation and determination of cause of death," she said.
"An investigation by the independent Corrections Inspectorate will also be carried out.
"As the man’s death remains subject to investigation, and the coroner is yet to determine the cause, we are limited in the amount of detail that we are able to provide."