MORGANTOWN, W.Va. (AP) â¿¿ State environmental regulators on Thursday issued two violations against a gas company and ordered it to stop all operations in West Virginia until the cause of a rig explosion that injured seven workers is determined.

The state Department of Environmental Protection cited the permit holder, AB Resources PA LLC of Brecksville, Ohio, for failing to comply with its permit plan and said those failures may have created the conditions that led to Monday's blast near Moundsville.

A telephone message to AB Resources was not immediately returned.

Union Drilling Inc. of Fort Worth, Texas, was sinking a well for AB Resources and another company, Dallas-based Chief Oil & Natural Gas, when it struck a methane pocket in an abandoned coal mine it had been drilling through. As the crew began to remove the drill string early Monday morning, the methane exploded.

What caused the ignition has yet to be determined, but a 50-foot column of flame continued to spew from the hole Thursday as the methane burned off and a team of rig-fire experts waited to cap it.

The DEP said the crew failed to set casing â¿¿ the steel pipe that seals off water and gas â¿¿ at the required depth. AB Resources also inaccurately reported the depth of the coal seam underneath its operation, the agency said.

DEP's order requires AB Resources to review the coal seam and casing depths for all its existing and proposed wells, to keep a person trained in blowout prevention on site at all times and to "demonstrate knowledge and an understanding" of what caused the explosion.

In the past two years, AB Resources has received 19 permits for operations in West Virginia, all of them in Marshall County in the Northern Panhandle. DEP Secretary Randy Huffman said his agency will review every active permit to be sure AB Resources is complying with state regulations.

Huffman also said his agency has begun a comprehensive review of its Division of Oil and Gas to see if any changes are required. It will look at staffing levels, funding, agency policies and the regulatory structure.

"Our goal is to prevent this from happening elsewhere," he said.

AB Resources is part of the growing rush to tap the vast natural gas reserves of the Marcellus shale field, a rich deposit the size of Greece that underlies Ohio, West Virginia, Pennsylvania and New York.

More than 500 Marcellus wells have already been drilled in West Virginia, Huffman said.

Although none of the companies involved in the Moundsville explosion had been charged with safety violations in West Virginia, federal records show that Union Drilling, based in Fort Worth, Texas, has paid $226,000 in fines for safety violations over the past five years.

The Occupational Safety and Health Administration did 20 inspections of Union Drilling operations around the country since February 2006, and 13 of those resulted in violations.

Union has not commented on the explosion, except to say it's cooperating with investigators.

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