At least eight people were killed in a methane blast in Raspadskaya, Russia's largest coal mine in West Siberia, a spokeswoman for the regional investigation department said on Sunday.
Natalya Ananyeva said investigators are now trying to establish the cause of the accident.
"It definitely was a blast. We are now trying to establish if the explosion was caused by firedamp or by pulverized coal," she said.
Russian energy ministry has set up a special group to deal with the aftermath of the blast.
According to previous reports, a total of 66 miners are trapped underground, and rescuers established contact with some of them. Four people are said to be injured in the blast.
An emergencies ministry officer earlier said the explosion occurred at 8:55 p.m. Moscow time (16:55 GMT). There were 359 people in the mine at the moment of the blast, 282 people were already taken to surface.
Russian emergencies minister Sergei Shoigu immediately informed Russian President Dmitry Medvedev about the blast and the rescue operation.
"Medvedev ordered the emergencies ministry head to report about the rescue efforts," and use every opportunity to rescue people, the Kremlin press service said.
A total of 12 rescue teams are currently involved in rescue efforts. Rescuers from neighboring regions have been put on alert and will arrive if necessary, the Kremlin said.
Russian Prime Minister Vladimir Putin discussed the accident with the region's governor, Aman Tuleyev.
Russian deputy energy minister, Vladimir Azbukin, is to visit the mine later on Sunday.
This is not the first deadly accident in the Raspadskaya mine, owned by a leading Russian coal producer. In late January, a worker was killed when ceiling collapsed in the mine.
On March 30, 2001, a methane blast killed four miners.
KEMEROVO, May 9 (RIA Novosti)
