The Department of Environmental Protection has allowed drilling to resume at a natural gas well pad in Lenox Twp. this week as it continues to investigate possible methane contamination of drinking water wells near a second Marcellus Shale well pad in the Susquehanna County township.

Cabot Oil and Gas Corp. resumed drilling a fifth natural gas well on the Zick pad on Monday after the driller's survey of homes and drinking water wells within about half a mile showed no elevated levels of methane, the agency and company said.

Cabot had voluntarily suspended operations at the site.

Bubbling in a pond on the Zick property that the department first described as "combustible gas" has stopped, a department spokeswoman said Thursday.

"The department's oil and gas program is continuing to evaluate conditions in this area," DEP spokeswoman Katherine Gresh said.

"At this time, the department has not made a final determination with regard to what impacts, if any, Cabot's earlier drilling may have had in the area."

The company and department also are evaluating the cause of elevated levels of methane found in three drinking water wells closer to a second Cabot well pad, the Stalter pad, in Lenox.

George Stark, a Cabot spokesman, said the company is gathering data and trying to determine the source of the methane even as the company's tests show the methane diminishing in the water supplies.

"We like the way it's trending," he said, "yet we will continue to monitor the three wells that did have an increase in methane."

Ms. Gresh said DEP samples collected at two of the water wells on Thursday continue to show methane in the open space above the water level in the wells.

DEP inspectors have also taken samples of the methane in the water and natural gas wells to evaluate their chemical fingerprints to see if they match.

The results of those tests "are not expected to be ready for a couple weeks," Ms. Gresh said.

State regulators have linked methane seeping into water supplies to faulty Marcellus Shale natural gas wells in several northeast and northcentral Pennsylvania counties, including a prominent case involving Cabot wells in Dimock Twp.

Cabot has denied it caused the methane contamination in that case, arguing that methane occurs naturally in water wells throughout the region.

Contact the writer: llegere@timesshamrock.com