HARRISBURG, Pa. — Pennsylvania environmental regulators say there’s a likely correlation between a natural gas company’s fracking operation and a series of minor earthquakes in western Pennsylvania last year.

The state’s Department of Environmental Protection revealed its findings Friday.

The quakes were recorded in April in Lawrence County, about 50 miles north of Pittsburgh and three-quarters of a mile from a natural gas well owned by Houston-based Hilcorp Energy. They were too weak to be felt by humans and no damage was reported.

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Fracking is a method to extract gas or oil from underground shale rock. It has been tied to earthquakes in neighboring Ohio and other states, but never in Pennsylvania, the nation’s No. 2 natural gas-producing state.

Hilcorp stopped fracking at the well pad after the quakes.