According to latest reports, 88 of some 200 miners had been rescued up to now from the Ulyanovskaya mine in Novokuznetsk, the largest coal producing center in the Kemerovo Region.
Rescuers are continuing work at the site. Earlier reports said Emergency Situations Minister Sergei Shoigu would soon fly to Novokuznetsk on President Vladimir Putin's order.
The Russian Prosecutor General's Office said a criminal investigation had been launched into the explosion.
The press service of the regional administration said the explosion was caused by the collapse of the mine roof and methane penetration.
Aman Tulyeve, the governor of the Kemerovo region, said the destruction caused by the explosion was hampering the rescue works.
"The main task at the moment is to rescue as many people as possible. The second task is to prevent a fire in the mine," he said.
Explosions are not uncommon in Russia's crumbling coal mining industry. But the Ulyanovksaya mine was only opened in 2002. It produces 3 million metric tons of coal annually and its reserves total 210 million metric tons.