WASHINGTON – Energy Department researchers so far have found “nothing of concern” in a study of whether chemicals used in hydraulic fracturing for natural gas at one site in Pennsylvania traveled toward shallower groundwater.

The preliminary evidence, if ratified in a final report, would bolster claims by the industry that the boom in drilling doesn’t pose risks to drinking water. Chances are low that fluids pumped more than a mile underground to free trapped gas could leak and contaminate drinking water, although that’s not the only hazard from the practice known as fracking, said Fred Baldassare, senior geoscientist at Echelon Applied Geoscience.

“A lot of us never thought there was much of a risk of fluid migration,” Baldassare, a former Pennsylvania Department of Environmental Protection official, said Friday in an interview. “We have so much confining pressure that the opportunity for water to move is just really minimal.”

The other dangers including methane gas that can migrate through fissures toward the surface much more easily, he said. Also, surface spills or leaks from containment ponds holding water that flows back from a fracked well also are a risk, he said.

The Energy Department’s study, which is still in progress and may be completed and released by the end of the year, is “far too preliminary to make any firm claims,” Shelley Martin, a spokeswoman for the National Energy Technology Laboratory, said Friday in an email. She declined to provide further information.

Richard Hammack, a scientist at the Pittsburgh lab involved with the study, didn’t return telephone and email messages. His statement that chemical-laced fluids remained thousands of feet away from drinking water supplies was published earlier Friday by the Associated Press.

“We are still in the early stages of collecting, analyzing and validating data,” according to a statement Friday on the laboratory’s website after the AP story was published.

Gas production in Pennsylvania surged in the past few years as companies expanded use of fracking, in which water, chemicals and sand are shot underground to break apart the rock and free the gas. The Marcellus Shale lies about 5,000 feet under in Pennsylvania.