The EPA has order the company to stop the flow of oil in Romeoville by noon Monday.
EPA spokeswoman Anne Rowan says the pipeline was leaking an estimated 200 to 600 barrels of crude per hour as of Friday.
Enbridge officials have said the leak is being contained as it comes out of the pipeline.
The company said the pipeline was moving about 459,000 barrels per day of heavy crude from Superior, Wis., to Griffith, Ind., when the leak started Thursday.
Earlier this summer, more than 800,000 gallons of oil leaked from an Enbridge pipeline into a creek about 60 miles southeast of Grand Rapids, Mich.