"A gas buildup and explosion in a Siberian coal mine on Thursday killed at least 52 people — including six rescuers — in the country’s worst mining disaster in over a decade, Russian officials said.

The accident occurred early in the morning at the Listvyazhnaya mine in the Kemerovo region of Russia, about 2,200 miles east of Moscow, after a ventilation shaft began filling with gas, Russia’s Investigative Committee reported.

Rescue efforts at the mine, which plunges 1,300 feet into the earth, continued throughout the day even as the death toll kept rising. Miners initially considered missing were gradually shifted to the list of the dead until late Thursday, when the authorities said they had been forced to suspend rescue operations because of a high concentration of methane in the mine."