At least four miners have died and four more are missing following an accident at a Russian coal mine.
Local authorities said the miners died underground of smoke inhalation, though it was unclear what the source of the smoke was.
But rescue efforts to locate the four missing miners have been hampered by high methane levels in the mine, Russia's emergencies ministry said.
A further 69 miners were able to escape the accident, the ministry added.
The accident happened at a coal mine in the Kuznetsk Basin region of Russia, in western Siberia.
It is one of the largest coal mining regions in the world, and was a powerhouse of the economy during the Soviet era.
Russia's coal mines have a poor safety record however, and Russia's President Vladimir Putin urged mine operators to improve safety standards when he announced a big increase in investment in the sector last year.
Russian news agencies said an investigation into what caused the accident was under way.