NZ Miners

Trevor Bolderson, a member and delegate of the Engineering Printing and Manufacturing Union (EPMU), said on Saturday that the chances of a second blast at the Pike River Coal mine were high after initial readings were taken of the gas levels in the mine.

"Gas samples taken at the mine are turning the wrong way and we are expecting that the second explosion may be forthcoming," he said.

"At the moment the rescue guys can't get into the mine because of this."

He said a number of families had congregated at a Red Cross centre in nearby Greymouth as the drama unfolded.

The miners were entombed after a powerful gas blast struck at the Pike River Coal Mine in Atarau, on South Island, on Friday.

A mission to locate the workers was hampered on Saturday by fears that dangerous gas could trigger a second explosion. It is not known if the men - who have now been missing for more than 24 hours - are alive or dead.

Two injured miners stumbled to the surface hours after the blast shot up the 108m ventilation shaft at the mine on Friday.

Construction, Forestry, Mining and Energy Union Queensland president Stephen Smyth said the two chemists would use the gas monitoring equipment to determine when the mine would be safe to enter.

"It's a terrible, terrible accident, very tragic," Smyth said. "When a coal mine goes bang, really the minutes and hours after it are the most important for people to get out because you've got the risk of secondary explosions."

Union general president Tony Maher said the Australian mine rescue experts that have been sent would be the best chance the miners had of survival, but it did not look good for them. "You've got to remember the Chile thing was a copper and gold mine. There's no explosive gases in those mines. Coal's got additional hazards. "If what's happened has been a methane and coal dust explosion, then... they've been disastrous in the past."

Maher said there was only a small number of Australians working in New Zealand mines. Two Australians are confirmed among the missing.

Asked if there had been any safety concerns about miners working in New Zealand, Maher said: "Mate, all mines are dangerous. I don't know if New Zealand is better or worse. We've had plenty of disasters in Australia."