Investigations into an incident which trapped 28 men in a Waihi mine's underground refuge chambers yesterday will start today.

The 15 men, and 13 of their colleagues in two other chambers who were rescued earlier in the day, were last night back with their families after the scare that shut down the Newmont Waihi Gold mine when a truck's engine caught fire.

The miners were tired but "all are in good spirits, they're very happy actually," said Waihi Gold general operations manager Glen Grindlay.

One man received medical attention for smoke inhalation, he said. There were no other injuries.


The 35-tonne Komatsu truck had burnt out while rescue teams sought to get to the trapped men, he said.

"We opted to go for the personnel first and worry about fire later".

The cause of the blaze was unknown, Mr Grindlay said.

"This will obviously be the focus of our investigation at a later stage."

The group had started a 12-hour shift at 7pm yesterday and were close to knock-off time when the fire started about 5am.

The men, who each carry individual rescue kits that include an oxygen supply, hunkered down in three separate refuge chambers designed to house trapped miners for up to 36 hours.

The chambers have water, a toilet and extra supplies of oxygen, along with decks of cards and reading material to keep miners occupied.

Thirteen of the men were evacuated by 10am, and the remaining 15 were freed shortly before midday.

The cause of the fire and the rescue operation is being investigated by the Department of Labour.

The Engineering, Print and Manufacturing Union (EPMU) called for urgent improvements to safety for underground miners, saying the Waihi fire was "the latest in a series of mine safety incidents since Pike River".

EPMU assistant national secretary Ged O'Connell said the industry must look to learn from the evacuation and emergency reaction.

"Particularly the fact that there has been no casualties ... it is a chance to get stuck in now and do a detailed debrief and learn as much as we can about the situation. Were there good procedures in place? Were people aware of them? Did they go with [the procedures]? How effective were they?"

Mr O'Connell said New Zealand should adopt the world-class practices of Queensland mines.

"The EPMU been on the ground this morning supporting the rescue effort and we're just relieved everyone is out safely and grateful to everyone involved in the rescue. Coming so soon after the tragedy at Pike River it was a little close for comfort," he said.

"The company, to its credit, has been very open and engaging with the union throughout the rescue and we are confident that there will be a thorough investigation to find out the cause of the fire, and check all health and safety procedures were followed properly."

The Department of Labour would not comment on details of its investigation, which could take six months.

Labour's health and safety spokesman Darien Fenton said the Government needed to address underground mining safety as a priority.

"While the Government has made some progress with its High Hazards Unit, New Zealand still has essentially the same mine safety regime as it did before the Pike River Mine tragedy," she said.