Chesapeake Energy Corp. has voluntarily suspended all completion operations in Pennsylvania as response crews work to contain a Chesapeake well blowout in the Marcellus Shale in northeast Pennsylvania.

The Bradford County well blew out late Tuesday night, and as of Thursday afternoon “well control efforts have been successful in significantly reducing flow from the leak,” said Chesapeake spokesman Brian Grove. Overnight, the company replaced well completion equipment at the site with equipment to seal the leak and said that work would continue through Thursday afternoon.

Oklahoma City-based Chesapeake was in the process of hydraulically fracturing (hydrofracking) the well when the blowout occurred, spilling hydrofracking fluid across the area, according to DEP.

Chesapeake said it does not yet know the cause of the blowout but said the “breach” occurred at a wellhead connection and “there is no evidence of a downhole casing failure of any type.” Chesapeake said the well “has emitted limited amounts of natural gas beginning early this morning,” but added that “gas plume modeling” by Chesapeake and emergency responders in Bradford County found that the emissions aren’t dangerous. No fires or injuries have been reported.

The amount and composition of the fluid released remains unknown. “All containment systems are now fully prepared to prevent fluids from leaving the location,” the company said. “Initial testing of area waterways has shown minimal impact, if any.”

The Pennsylvania Department of Environmental Protection (DEP) is on the scene as well. “The focus at this time is to get the well killed,” DEP spokesman Dan Spadoni told NGI‘s Shale Daily.

Because of the chemical additives in hydrofracking fluids, Spadoni said that DEP is “doing sampling of some nearby home drinking water wells, as well as some different surface locations, including Towanda Creek and an unnamed tributary to Towanda Creek,” but it didn’t have any test results as of this morning.

Boots & Coots, a Texas well control specialty company, was on the scene Thursday, according to officials.

The blowout took place in the small rural community of Leroy, prompting seven families to initially evacuate the area.