Officials said the concentration of methane in the mine was rising and that fires were burning deep underground.

The death toll from the explosions has risen to 66, the Russian emergencies ministry said.

Many victims were rescue workers killed by a second explosion hours after the first one struck late on Saturday.

The second blast ripped apart the coal mine's ventilation shaft and damaged buildings on the surface.

"Our task now is to put out the fires and reduce the gas concentration, and only after this is done will we send people," said emergencies ministry official Pavel Plat.

The mine, in the town of Mezhdurechensk in the Kemerovo region, is about 3,500km (1,900 miles) east of Moscow.

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