A methane leak exploded and killed 12 coal miners in a Polish pit today.

High levels of gas forced rescuers to suspend their search for 15 miners missing more than a half a mile underground today, and the Polish president said conditions were “getting worse” for anyone trapped and still alive.

Fear of a second gas explosion was slowing efforts to find 15 Polish coal miners missing 3,300 feet underground after a blast that killed at least eight of their colleagues.