The U.S. Environmental Protection Agency is projecting that the amount of oil that spilled from a pipeline owned by Enbridge Energy Partners could be higher than originally estimated as concerns rise that the oil will reach Lake Michigan. Enbridge Energy (NYSE: EEP) had estimated the amount of oil leaked into the Kalamazoo River to be around 800,000 gallons. But the EPA believes that number may actually be closer to 1 million gallons. Enbridge Energy Partners, the Houston affiliate of Calgary, Alberta-based Enbridge Inc. (NYSE: ENB), owns the 30-inch Lakehead System pipeline, which is capable of transporting 190,000 barrels a day and runs from Ontario to Indiana. It remains shut down for now. The underground pipeline began leaking on the morning of July 26 and was shut in by July 27. However, response crews are still working to contain the spill, said to be the largest in the history of the Midwest. By early afternoon on Thursday, shares of Enbridge Energy were down 4.9 percent to $54.02 in heavy trading after having fallen as low as $53.25. The EPA assumed the role of federal on-scene coordinator for the incident. The agency has responsibility under the Oil Pollution Act of 1990 for the spill because it happened inland, rather than offshore. â¿¿This is a serious spill that has the potential to damage a vital waterway and threatens public health,â¿ the EPA said in a statement. The spill has affected up to 25 miles of the Kalamazoo River and residents of more than 30 nearby homes reportedly had to be evacuated. Michigan officials are upset because they question when the leak actually began and what they consider to be a slow response from Enbridge. On Wednesday, the Houston company said it was doubling its 150-person work force in Michigan and boosting the size of its booms to 31,000 feet from 14,000 feet. â¿¿While the oil leak has stopped, this incident is far from over,â¿ the EPA said, adding that its focus is currently on preventing the oil from affecting â¿¿sensitive shorelinesâ¿ and keeping it out of the Great Lakes.