CHARLESTON, W.Va. -- An Ohio gas company involved in a drilling rig explosion that injured seven workers is clear to resume operations in West Virginia

The West Virginia Department of Environmental Protection began reviewing 19 permits it had issued to AB Resources of Brecksville, Ohio, after the June 7 blast near Moundsville.

DEP spokeswoman Kathy Cosco said Thursday the company complied with the conditions of the cease-operations order and corrected all underlying violations.

Texas-based Union Drilling Inc. was sinking a well for AB Resources when it hit methane in an abandoned coal mine.

Cosco says what caused the methane to ignite remains unclear and may never be determined.

An investigation by the U.S. Occupational Safety and Health Administration is continuing.