The blaze took place in the Kemerovo region in southwestern Siberia.
Russia’s state Tass news agency reported, citing an unnamed emergency official, that coal dust caught fire, and that smoke quickly filled the mine through the ventilation system.
A total of 285 people were in the mine at the time of the incident, 237 of them have been evacuated.
Efforts to rescue the rest are still ongoing, hampered by large amounts of smoke.
Russia’s Investigative Committee has launched a criminal probe into the fire on charges of violating safety regulations that led to deaths.