Canadian pipeline company Enbridge Energy Partners confirmed that a pipeline on its Lakehead system leaked near a pump station in Marshall, Mich.
"Enbridge is treating this situation as a top priority," said Enbridge President Terrance McGill in a statement. "We are bringing all available resources to bear -- ranging from emergency response and containment personnel to environment and water quality specialists."
Roughly 20,000 barrels of oil spilled into an area creek and Enbridge confirmed the spill had reached the Kalamazoo River by Monday evening, area broadcaster WOOD TV 8 reports.
Two homes in the area were evacuated and officials warned residents against swimming or fishing in the Kalamazoo River. Emergency officials said there was no threat to drinking water, the report adds.
Enbridge workers were inspecting parts of the pipeline during the leak. The company said it was dispatching containment boom and skimmers to the area to control the spill.
The Lakehead oil pipeline system is one of the longest in the world at 3,100 miles.