Three security guards employed by a UK-based company bidding to run Auckland Central Remand Prison at Mt Eden, have been arrested after the death of a man they were deporting from Britain.
Jimmy Mubenga, 49, from Angola, became unwell on a British Airways flight preparing to leave Heathrow airport. He died on 12 October.
The BBC has reported that passengers on the plane said he had been restrained and was struggling to breathe.
Three G4S security guards were arrested, but the Metropolitan Police says that does not necessarily mean they will be charged.
The company says it is helping police with their investigation into the man's death.
It says he became unwell while being escorted on the plane.
G4S says cabin crew were alerted and the aircraft returned to the terminal.
Mt Eden contract bidder
G4S is one of three companies bidding for a contract to manage Mt Eden prison.
Two years ago in Australia, a man died from heat stroke in one of the company's prison vans, which had no air conditioning.
A coroner found the company, two prison van drivers and Australia's Department of Corrective Services were all responsible.