Efforts to reach at least 29 coal miners missing after an explosion at an underground mine in New Zealand have stalled as fears of another blast frustrated rescue attempts.
Police said the explosion at the coal mine on the South Island's west coast appears to have damaged the mine's ventilation system.
Locals said they are drawing hope from the rescue of 33 miners in Chile last month.
Two miners survived the blast at the Pike River mine but there has been no contact with any others, the mining company's chief executive said.
Police said a specialist mine rescue team is at the scene but could not go underground because the blast knocked out power to the mine's ventilation pumps, meaning there was a danger they could ignite trapped gases.
'There's been an explosion, they don't know what's caused it, they can't just go charging in there and put other people at risk,' police spokeswoman Barbara Dunn told Radio New Zealand.
The ventilation system would also normally supply air to any surviving miners, and police said they are concerned that it had been compromised by the power outage.
Families of the miners have gathered at the site, at the heart of New Zealand's coal industry about 50km northeast of Greymouth.
Grey District mayor Tony Kokshoorn said the rescue was difficult and could take days. But he added, they were 'holding on to hope'.
Pike River Coal chief executive Peter Whittall said the miners were about 120 metres beneath the surface.
They had started the afternoon shift about an hour before the blast. Mr Whittall said there had been no confirmed fatalities.
The mine, which began production last year, has a 2.4km access tunnel running beneath the Paparoa mountain range to the coal seam.
Ambulances, medevac helicopters and rescue workers are on the surface ready to treat any injured miners, with ambulance officers saying they are preparing for a long operation.
Mining Minister Gerry Brownlee said the government would put whatever resources are needed into rescuing the miners.
Pike River is jointly owned by New Zealand Oil & Gas and two Indian companies - Gujarat NRE Coke and Saurashtra Fuels Private Ltd.
Meanwhile, it is understood that two men from Yorkshire and one man from Scotland are among the trapped miners.
