The lead agency investigating the deaths of two foreign seamen on a logging ship in Northland says confined-space incidents are becoming too common in the industry.
The two men, one from South Korea and the other from Myanmar, suffocated to death on Monday aboard the Panamanian-registered TPC Wellington at Marsden Point near Whangarei, and a third man had to be treated in hospital.
Emergency services say one of the men entered a hatchway to check for a possible leak, and the other two followed in a failed rescue attempt.
The head of the investigation for the Transport Accident Investigation Commission, Captain Iain Hill, says the key thing they want to find out is why the men were in the hold, which was full of timber.
Captain Hill hasn't ruled out the possibility that metal bromide, a chemical used to fumigate logs, was a contributing factor to the men's deaths.
The commission is rushing to complete the investigation before the vessel's scheduled departure on Wednesday.
Police plan to speak with third crewman
Police say the third crewman is back on the ship, after being discharged from Whangarei Hospital, and they plan to speak with him.
They have not released the names of the dead seamen, saying they are attempting to contact relatives in their home countries.
The Maritime Union of New Zealand says the accident is one of the most serious in the industry in recent years.
Spokesperson Victor Billot says the union is sending an inspector to the vessel to investigate whether there are any other safety hazards on board. He says he has concerns that safety standards on foreign vessels are often not up to scratch.
Maritime Union president, Gary Parsloe, says there is still no clear picture of what happened, and the union wants to know whether there was enough breathing gear for the workers.
Mr Parsloe says the union also wants to know whether they'd had proper instructions about safety procedures and standards.