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Fracking can affect drinking water supplies in certain circumstances, the Obama administration said in a long-awaited report issued Tuesday, leaving open the possibility of more widespread impacts that it says can’t be determined with current data.

The report, written by Environmental Protection Agency scientists, includes findings that are more open-ended than those in a draft version last year, when the agency said fracking, or hydraulic fracturing, isn’t having “widespread, systematic impacts on drinking water.”

The final report doesn’t include that phrase because EPA scientists determined they couldn’t back it up without comprehensive data on hydraulic fracturing across the U.S. and because it didn't “really communicate the findings in the report,” said Thomas Burke,deputy assistant administrator at EPA on a conference call with reporters Tuesday.

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The report is one of a number of actions supported by environmentalists that the Obama administration has taken in its final weeks in office, including denying a permit for a stretch of the Dakota Access Pipeline.

In its draft report on fracking, the EPA said the cases of contamination it found “were small compared to the large number of” fracked wells in the nation. The final report says more broadly that the agency has scientific evidence that fracking activities “can impact drinking water resources under some circumstances.” When asked, Mr. Burke did reiterate the report’s earlier findings that the EPA found only a small number of cases of contamination but stressed the lack of data.

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