A string of inquiries is under way into how a healthy 25-year-old inmate died after a five-hour journey between prisons.
The inmate's life support was turned off about 3pm on Thursday after his family watched his life slip away over the fortnight that passed since he suffered a collapsed lung.
Corrections regional commissioner Jeanette Burns said two internal investigations were under way to understand how the prisoner had become unwell.
She said he was transferred by van from Mt Eden Prison to Northland Prison near Kaikohe on May 29.
The man was checked by nurses on arrival - part of a normal prison transfer routine.
However, she said the man reported feeling unwell the next morning. Nurses were advised to take him into Kaikohe for a check-up by a doctor, who then advised he be sent to hospital in Whangarei.
Arriving at the hospital, the man was still in pain but able to walk without assistance.
"That's where it all started to go wrong," Ms Burns said.
The Herald has been told the man was identified as having a collapsed lung, which was inflated by medical staff.
He was later found to have an infection, which led to pneumonia and eventually to his death.
Ms Burns said the man was still a prisoner at the time of his death so an inquiry would be carried out into his "death in custody".
It would be investigated from a medical perspective and by the prison's investigation inspectorate. The death had also been referred to the coroner.
She offered condolences to the family and was expecting to meet the man's parents through National MP Mark Mitchell.