A malfunction at BP's Whiting Refinery in Indiana caused oil to spill into Lake Michigan.
BP spokesman Scott Dean said the disruption was discovered around 4:30 p.m. Monday. It resulted in the discharge of crude oil from the refinery's cooling water outfall into the cove between the waste water treatment plant and the steel mill.
It's not clear how much oil spilled into the water, but Dean said the sheen was no longer visible in the water Tuesday morning.
"The discharge has stopped," Dean said, "and BP and its response team have deployed boom, containing the oil to a cove."
There were no injuries, he said, and cleanup activities are underway.
NBC 5 Chicago's Sky5 helicopter footage of the scene showed crews cleaning up the lakeshore near the refinery. State and federal environmental officials also were at the scene.
Dean said BP notified the U.S. Coast Guard, U.S. EPA and the Indiana Department of Environmental Management after the discharge was discovered.
"BP will continue to work in full cooperation with the agencies to ensure the protection of personnel, the environment and surrounding communities."
In a joint statement, Sens. Mark Kirk and Dick Durbin said they are encouraged to hear the spill is contained but are "extremely concerned" about the possibility of a future spill after BP recently announced a plan to nearly double its processing of heavy crude oil at the refinery.
"We plan to hold BP accountable for this spill and will ask for a thorough report about the cause of this spill, the impact of the Whiting Refinery’s production increase on Lake Michigan, and what steps are being taken to prevent any future spill.”