Pennsylvania environmental regulators want to determine whether a series of minor earthquakes in the state this week were caused by nearby fracking operations.
Five tiny temblors took place in a 22-hour span in Lawrence County, about 50 miles north of Pittsburgh and three-quarters of a mile from a natural gas well. No damage was reported.
A spokesman for the Pennsylvania Department of Environmental Protection says a probe is ongoing. He didn't say what action regulators would take if the driller, Hilcorp Energy, is found to have caused the tremors.
The privately held oil and natural gas producer did not return a call for comment.
Hydraulic fracturing has been tied to earthquakes in neighboring Ohio and other states, but never in Pennsylvania.