The Environmental Protection Agency (EPA) is once again facing criticism from oil and natural gas companies over its controversial findings in Wyoming, in which a draft study links hydraulic fracturing to ground water contamination, and the agency's move to test water samples in Dimock, Pa.

EPA regulator Jim Martin, the head of EPA's Wyoming office testified on Capitol HillĀ  -- the same hearing at which Gasland documentarist Josh Fox was arrested -- and said the EPA stands by its study but offered a warning: the study's conclusions may only be relevant to Wyoming.

I draw your attention to the careful language with which our conclusions are couched. We make clear that the causal link to hydraulic fracturing has not been demonstrated conclusively, and that our analysis is limited to the particular geologic conditions in the Pavillion gas field and should not be assumed to apply to fracturing in other geologic settings, read Martin's submitted testimony before the House Science Committee, as published by political blog, The Hill.

Encana Corp., the natural gas company operating the wells in Wyoming strongly questioned the accuracy of the EPA's findings and questioned the agency's methodology.

Did EPA Study Measure Natural Hydrocarbon Levels?

The company's main argument questions whether or not the EPA was registering in its findings hydrocarbon levels that were naturally present in ground water, which the company said is to be expected in a region where hydrocarbons, like methane, naturally bubble up from the ground.

Encana is not the only company commenting on the EPA. Cabot Oil & Gas in recent weeks has heavily criticized the EPA for cherry-picking data to justify its testing of town water samples, according to Gas Business Briefing

Based on this reexamination, it appears that EPA selectively chose data on substances it was concerned about in order to reach a result it had predetermined. EPA chose to include specific data points without adequate knowledge or consideration of where or why the samples were collected, when they were taken, or the naturally occurring background levels for those substances throughout the Susquehanna County area, read a statement from Cabot.

At townspeople's request, the EPA started testing water samples after regulators noticed amounts of toxic chemicals were present in the water wells of several residents. They agency has also resumed the delivery of water shipments to those who refuse to drink their well water for fear of pollution.

Our priority is the health of the people there, and our actions are guided entirely by science and the law, the EPA said last week.