A methane gas leak and explosion at a Siberian coal mine killed at least 52 people on Thursday, including six rescuers, Russian officials said.

The big picture: Russia's worst mining disaster in more than a decade occurred at the Listvyazhnaya mine in the Kemerovo region after gas filled a ventilation shaft, suffocating workers there, per the New York Times.

• The Russian Investigative Committee said in a statement it has opened a criminal investigation into Thursday morning's disaster.
• The mine's director and his deputy have been arrested on suspicion of violating safety rules, the agency said.
• Authorities announced later in the day they were suspending rescue operations due to "high concentration of methane in the mine," the NYT reports.

By the numbers: 285 people were in the mine some 820 feet underground when the disaster struck, according to AP.