A gas explosion at a coal mine in eastern Iran’s South Khorasan province has killed at least 51 people. State media reported that the blast, caused by a methane gas leak, occurred at the Madanjoo mine in Tabas at 9 p.m. local time yesterday.

There were 69 workers in two blocks of the mine when the explosion occurred. More than 20 workers were injured, and it remains unclear how many are still trapped underground. The death toll has been revised upward from an initial report of 30 fatalities.