CHEYENNE, Wyo. (AP) - A U.S. Environmental Protection Agency official is defending a draft EPA report that theorizes gas industry activity including hydraulic fracturing may have polluted groundwater in Wyoming.

EPA Regional Administrator James Martin told a U.S. House subcommittee hearing in Washington on Wednesday his agency isn't saying the report applies to fracking elsewhere, such as the Marcellus Shale in the northeast.

Republican Rep. Ralph Hall of Texas countered that the December report is but one example of the EPA "going after fracking everywhere it can."

Petroleum companies frack their wells to improve the flow of oil and gas. They pump water, sand and chemicals down well holes to fracture deposits.

Environmentalists have raised concern about fracking for years. The petroleum industry says there are no proven cases of fracking polluting groundwater.