At least 40 miners have died and a dozen more are trapped underground after an apparent gas explosion in a pit in Russia, officials say.
The missing miners are said to be about 700 metres below ground
The blast, possibly caused by leaking methane, happened in the Taizhina coal mine in Siberia.
Some miners have reportedly been rescued or have made their own way to the surface; rescue teams are searching for seven possible survivors.
Russia's coalmines are notoriously under-funded and prone to accidents.
The blast happened in the early hours of Saturday morning in the Kemerovo region of Siberia, about 3,000km (1,850 miles) east of Moscow.
The missing miners are believed to be trapped around 700 metres (2,200 ft) underground, although no contact had been established with them.
Kemerovo's governor, Aman Tuleyev, arrived at the scene to co-ordinate rescue efforts.
He told the NTV television station that the shortest path to the blast site was blocked by rubble.
He said that rescuers were now attempting to reach the trapped miners by burrowing through from an adjacent mine.
The explosion is the third fatal mining accident in the area in the last two years.
In September 2002 the roof of a ventilation shaft collapsed in the same mine, killing one and seriously injuring two other miners.
In June last year, a methane gas explosion at another mine in the area killed twelve.
Russian mining has suffered from a funding crisis since the collapse of the USSR.
The BBC's Stephen Dalziel said that this shortage of investment had led to shortcuts being taken in safety procedures and an increase in accidents.