Pennsylvania Attorney General Josh Shapiro on July 22 said he was charging the National Fuel Gas Supply Co., a unit of National Fuel Gas Co. and subcontractor Southeast Directional Drilling LLC with environmental crimes.

"These companies are being charged for polluting an unnamed tributary and groundwater in Washington County," Shapiro said in a social media post.

Last month, a state grand jury's report highlighted the failure of government agencies to oversee the oil and gas fracking industry and protect residents from the inherent risks of industry operations.

The report followed previous criminal findings against two E&P companies—Range Resources Corp. and Cabot Oil & Gas Corp.—for repeated violations of Pennsylvania environmental laws.

Fracking—and horizontal drilling techniques—have produced massive amounts of natural gas and oil in the U.S. over the past decade.