Greymouth: Fears over poisonous or combustible gases were preventing rescuers entering a mine in New Zealand where 29 men are missing after an explosion, according to police.
A specialist mine rescue team was on standby at the Pike River coal mine on Saturday but would not go underground until tests confirmed there had been no build up of gases in the wake of Friday`s blast, police commander Gary Knowles said.
There has been no contact with the men since the explosion at the remote mine and Knowles said rescuers were hoping to swing into action in the next 24 hours, once air samples from the mine had been analysed.
"To date we have not had an opportunity to get underground, we`re still waiting for a window of opportunity to do this," he told reporters, adding that a mixture of subterranean gases and coal dust could trigger another explosion.
"As the search commander I`m not prepared to put people underground until we can prove it`s a safe environment."
Mine owners continued to hold out hope the missing men were still alive, although Grey District Mayor Tony Kokshoorn conceded "every hour that goes by, it gets more dire".
Prime Minister John Key said every effort was being made to reach the miners, who range in age from a 17-year-old, believed to be on his first shift, to a 62-year-old.
"It`s a difficult time for everyone but we`re determined to get the men out alive," he said.
Key said expressions of support had poured in from around the world, including a personal e-mail from Prince William saying his heart and thoughts went out to the miners.
The missing miners are believed to include at least two Australians and three Britons, as well as New Zealanders.
They are thought to be only about 150 metres (500 feet) from the surface but 2.5 kilometres (1.5 miles) from the mine entrance in a tunnel that runs beneath the Paparoa mountain range to the coal seam.
Special equipment was flown in from Australia to test gas levels in the mine and Australian Prime Minister Julia Gillard said her government would meet any requests for assistance.
Gillard said the world had already seen one "miracle" mine rescue this year, referring to the successful retrieval of 33 men trapped underground for 69 days at a mine in Chile.
"The world has witnessed a mine disaster already this year, and a miracle when people came out alive, and so our very best wishes go to the New Zealanders as they deal with this situation," she said from the Portuguese capital Lisbon, where she is attending a NATO summit.
Pike River chief executive Peter Whittall said fresh air was being pumped into the mine and it was possible the miners had reached a safety refuge.