Three workers were hurt in north-central West Virginia early Friday when a spark from a natural gas drilling operation ignited methane gas hundreds of feet underground.
Two of the workers were airlifted to a hospital and the third worker returned to the job site around 9 a.m.
The spark sent up a fireball and triggered a blaze that burned for about an hour on the floor of the rig, according to officials.
The fire took place at the Antero Resources site near Sycamore in Harrison County.
Antero voluntarily shut down the operation, and a DEP investigation is under way.