An Australian mining safety expert says there will be difficulties ahead as authorities go about retrieving bodies from the Pike River Coal mine.
David Cliff from the Minerals Industry Safety and Health Centre at the University of Queensland specialises in coal mining and underground fires.
He says the explosion would have weakened mine structures and left dangerous build-ups of carbon dioxide and carbon monoxide.
He says authorities will probably need to make the gases inside the mine inert before they seek to re-enter the mine to retrieve bodies. This could be done by directing nitrogen, or the exhaust from a jet engine, into the mine.
But he says it may not be possible to recover the bodies.
Mr Cliff says he is not surprised at the second explosion, which would probably have been caused by exploding methane gas, creating temperatures of more than 1000 degrees Celsius.
Another Australian mining expert says many more tests will need to be taken at the mine before there is any chance of recovering the miners' bodies.
Gavin Mudd, an environmental engineering lecturer at Monash University in Melbourne, says authorities will need to test the chemical composition of the air and try to work out how much damage has been done to the mine's structure.
He says that work will be similar to tests under way since Friday.
Engineering, Printing and Manufacturing Union president Andrew Little says the mine will be purged with carbon dioxide, allowing emergency services to recover the miners' bodies.
Equipment will be brought in from Australia to purge the mine, and he expects the bodies will be recovered in a day or two.
