Russian news agencies say the death toll from two methane gas explosions at a coal mine in western Siberia rose to 52 Tuesday.
Authorities say 38 miners are still missing, and that those who may still be alive in the mine are threatened by rising water levels.
Russian Prime Minister Vladimir Putin met with injured miners at a hospital in the Kemerovo region of Siberia. He also has visited the Raspadskaya coal mine to inspect the rescue operation, and has demanded a "detailed investigation" into the accident.
The missing miners were believed to have been trapped some 500 meters below the surface.
Among those killed were 19 rescue workers who had ventured into the vast network of tunnels before the second explosion.
Russia's emergency situations minister, Sergei Shoigu, said the blasts, which occurred several hours apart late Saturday and early Sunday, destroyed pumps that remove water from the huge mine.
Mine accidents are relatively common in Russia, where mining infrastructure is old and safety code enforcement lax.
Some information for this report provided by AP, AFP and Reuters.