The mine was evacuated on Wednesday evening after a roof convergence disrupted ventilation.
The next morning a drill rig was intended to intersect a worked-out area of the mine as part of the plan to address the conditions underground.
ARP said the rig caught fire at about 4.45am when the drill was about 420 feet below the surface and 300ft above the mine workings.
After the incident, the company said it was developing a plan with safety authorities for constructing seals to isolate the mine area affected by the roof convergence.
“Although operations at Warrior will remain idled until it is safe to resume production, mine personnel do not presently anticipate mine production to be idled for an extended period,” ARP said.
Kentucky state spokesperson Linda Potter told ILN last week that the drill had hit and ignited a pocket of gas.
Late last week ARP said the other injured worker remained under observation.
The Warrior Coal complex, which includes the underground Cardinal mine, employs about 400 workers and produced 6.2 million tons in 2009. Warrior opened in 1985 and was acquired by Alliance in February 2003.
