State environmental regulators are investigating high levels of methane in a Dimock Twp. water well in an area of the community still off-limits to some natural gas drilling operations because of a past methane incident.

The Department of Environmental Protection began the investigation last week after it received a complaint of turbid water in a private well and later found "high levels" of methane dissolved in the water and airborne gas accumulating in the well, spokeswoman Colleen Connolly said.

Tests at four other water wells did not show elevated levels of the gas, she said, but the state plans to continue monitoring.

The home is near the Costello and Gesford well sites operated by Cabot Oil and Gas Corp. that the state is evaluating as part of its investigation, she said. It is also in a 9-square-mile area where the DEP has barred Cabot from drilling new wells until methane the state first linked to the company's operations in 2009 subsides in 18 water supplies.

The water well now being investigated was not part of the earlier incident, Connolly said.

Cabot spokesman George Stark said crews discovered that a line that vents shallow methane from the Costello well was frozen during a recent period of cold weather. Since the plug was cleared, levels of gas in the water well have decreased.

"It appears to be a small and localized event," he said and added that Cabot will now monitor all its vent lines during extreme weather events.

The company is providing the home with bottled water.

The Gesford wells being evaluated were hydraulically fractured, or fracked, in November after the state lifted some of its restrictions on Cabot's operations in the area. The process of injecting chemically treated water and sand into rock formations at high pressure releases the gas trapped in the shale.

Fracking has not been implicated in gas migration incidents in the region. Instead, past problems have been tied to faulty construction of gas wells.

Contact the writer: llegere@timesshamrock.com