The mine where the explosion occured is operated by a company called Apatit, a major Russian producer of the phosphate mineral apatite used in making fertiliser. Apatit is part of the PhosAgro fertiliser group.
Russia's mining safety watchdog, Rostekhnadzor, said it had launched an investigation into the blast at the Rasvumchorrsky mine. An operation to retrieve bodies was under way.
Last year 110 people died in a blast in a mine in Siberia - Russia's worst mining accident in recent years.