The EPA said late Tuesday it issued a notice of federal interest to BP following the release of an unknown volume of oil into Lake Michigan from its Whiting refinery in Indiana.
BP notified federal authorities of the incident late Monday but it wasn't until late Tuesday that public information was released.
The environmental regulator said the notice to BP directs the company on how to respond to the release. The company, acting under EPA oversight, deployed more than 2,000 feet of containment boom and vacuumed up about 120 barrels of an oil-water mixture from the incident site.
"BP crews also are combing a nearby company-owned beach for oil globs and conducting air monitoring to ensure the safety of the public," the EPA said. "The U.S. Coast Guard has flown over the area and has not observed any visible sheen beyond the boomed area."
The Whiting refinery, which started operations in 1889, is the sixth-largest refinery in the United States. It processes on average 413,000 barrels of raw crude oil per day.
There was no statement from BP on the incident and the cause of the release is under investigation.