MOUNDSVILLE, W.Va. -- Seven people were injured early today in an explosion at a two-day-old gas well that had recently started drilling to the deep Marcellus shale formation in rural West Virginia.

All the injured were taken to the burn unit at West Penn Hospital in Pittsburgh for burns to their arms and legs.

Kathy Cosco, a spokeswoman for the West Virginia Department of Environmental Protection, said initial reports indicate the drilling may have gotten into the Alexander Mine and hit a pocket of methane gas. She said the Alexander Mine is inactive and owned by Pittsburgh-based Consol Energy.

Thomas Hart, director of emergency services for Marshall County, said crews from 20 fire departments are on the scene in a remote area outside Moundsville as flames continue to shoot 50 feet into the air. Fire crews are keeping the flames from spreading to equipment on the drilling site, but they are waiting for experts to be sent from well owner Dallas-based Chief Oil & Gas of Wexford, Pa., for help with extinguishing the fire. The rigging was extensively damaged.

A total of seven workers from BJ Tubular Services, of Houston, Texas, and Union Drilling, a West Virginia firm, had been working on the well when it exploded at 1 a.m. Two of the injured workers were employed by BJ Tubular and five by Union Drilling, said Kristi Gittins, a spokeswoman for Chief Oil & Gas, which has drilled approximately 15 Marcellus shale gas wells in West Virginia and 50 in Pennsylvania.

The well was permitted to AB Resources of Brecksville, Ohio, the operator, but owned by Chief Oil & Gas. Ms. Gittins said the well drilling had progressed to about 1,000 feet deep, on its way to the Marcellus shale formation about 8,000 feet below the surface.

"Nothing we did was unusual or unexpected. What caused the fire has yet to be determined, but you can hit pockets of gas, that's not uncommon," Ms. Gittins said. "We had it contained fairly quickly, the area was secured, there was no evacuation and the damage was limited to the (well) pad site."

Ms. Gittins said the well, the second to be drilled on that pad, was still "flaring," or burning, gas at noon, "which is what you want to happen." She said she didn't know how long the well flaring would continue.

Marcellus shale formation lies 5,000 to 8,000 feet deep under three-quarters of Pennsylvania and parts of New York, Maryland, Ohio and West Virginia, a total of 95,000 square miles. Estimates of the amount of extractable gas it contains have risen from 25 trillion cubic feet a year ago to up to 75 trillion cubic feet today.

The West Virginia explosion is the second major accident at a Marcellus shale drilling operation in four days. On Friday, natural gas and drilling fluids escaped from a Marcellus shale well operated by EOG Resources in Lawrence Township, Clearfield County, Pa., for 16 hours, threatening to pollute a nearby stream.

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