State environmental officials and expert firefighters brought in by Chevron have been continuing to monitor a burning Marcellus Shale natural gas well in southwestern Pennsylvania.
The well about 50 miles south of Pittsburgh in Dunkard Township erupted into flames shortly before 7 a.m. Tuesday, injuring one worker and leaving one still unaccounted for early Wednesday.
State Department of Environmental Protection officials say the fire may burn for days, delaying efforts to determine its cause.
DEP spokesman Jon Poister says experts from Houston-based Wild Well Control arrived on the site Tuesday evening to begin working out a plan to extinguish the fire.
The Texas company specializes in responding to well site fires around the country, including one in Indiana Township, near Pittsburgh, that killed two welders in July 2010.
