The Chesapeake Energy Corporation lost control of the well site near Canton, in Bradford County, around 11:45 p.m. Tuesday, officials said. Tainted water continued to flow Wednesday afternoon, though workers finally managed to prevent any more of it from reaching the stream.
No injuries were reported, and there was no explosion or fire.
Chesapeake said a piece of equipment failed late Tuesday while the well was being hydraulically fractured, or fracked. In the fracking process, millions of gallons of water, along with chemical additives and sand, are injected at high pressure down the well bore to break up the shale and release the gas.
State environmental regulators were taking water samples from the tributary of Towanda Creek, which is stocked with trout.
The blowout comes amid a natural gas drilling boom in the Marcellus Shale formation.