A new study out of Penn State University says at least three wells in Bradford County, Pennsylvania have been contaminated with toxic fluids as a result of drilling and hydraulic fracturing for natural gas in the Marcellus Shale play.

The study says the wells were contaminated with dangerous levels of methane and other substances in 2010.

Researchers say the toxic fluid probably escaped while wells were being drilled, but the study does not implicate the fracking technique itself.

Chesapeake Energy has been involved in several investigations by Pennsylvania environmental regulators and had been levied a million dollar fine in 2011.

The Penn State study was published May 4 in the Proceedings of the National Academy of Sciences.

Researchers say it’s believed that drilling fluid escaped through uncased boreholes.

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