WASHINGTON (Reuters) - A fireball and explosion burned seven members of a crew drilling for natural gas at an abandoned coal mine in West Virginia on Monday, the second big fire at an energy formation known as the Marcellus Shale in less than a week, a government worker said.
"Seven workers were taken to the hospital for burns," Prentice Cline, an Occupational Safety and Health Administration assistant in Charleston, West Virginia said.
Local media reports said the injuries were not life-threatening.
Cline said five of the workers work for Union Drilling, Inc, headquartered in Fort Worth, Texas, and two work for BJ Services Co of Houston.
AB Resources PA LLC of Brecksville, Ohio is the operator of the well, while privately-held Chief Oil & Gas, holds responsibility to drill and complete the well, local media reports said.
Chief was unavailable for comment.
The vast Marcellus Shale field runs through West Virginia and Pennsylvania. On Thursday, a well operated by EOG Resources Inc in Pennsylvania blew out when a drilling team lost control of it while preparing to extract gas using the hydraulic fracturing technique.
Kevin Book, an analyst at ClearView Energy Partners, said it appeared West Virginia fire was also caused by workers getting ready to use hydraulic fracturing or "fracking" to get to the gas.
Local media reports said the natural gas drilling operation near Moundsville was less than a week old.
Union Drilling, Chief's site contractor, had drilled the first 1,000 feet of a second well on the property and was preparing to install surface casing when crews apparently hit and ignited the methane, local reports said.
Critics of fracking say domestic water supplies are contaminated by chemicals that are forced into the ground along with sand and millions of gallons of water to free gas from fissures in the shale a mile or more underground.
(Reporting by Timothy Gardner and Eileen Moustakis in New York;Editing by Sofina Mirza-Reid)