The blast occurred 1,850 miles east of Moscow, and was apparently caused by a methane buildup, according to an emergency spokeswoman.

At the time of the explosion, 103 miners were working under the surface, she said. Rescuers evacuated 90 miners and recovered 13 bodies.

Rescuers had to suspend the salvage effort at one point due to a high concentration of methane, but resumed work when it subsided, she said.