CALGARY, Alberta, Jan 14 (Reuters) - Enbridge Energy Partners LP (EEP.N) said it has restarted a section of oil pipeline on its Lakehead system in North Dakota after repairing a leak that it detected on Friday.

Enbridge Energy, an affiliate of Canadian pipeline operator Enbridge Inc (ENB.TO), said it will run line 2B at 80 percent of its normal operating pressure while the company and regulators determine the cause of the break.

The pipeline is part of the massive system that transports most Western Canadian oil to the U.S. Midwest, Oklahoma and southern Ontario. The line that was damaged extends to Superior, Wisconsin, from Cromer, Manitoba. Its capacity is 440,000 barrels a day.

The company had rerouted the supply onto other lines on the system after discovering the leak, which spilled about 3,000 barrels of oil in Pembina County, North Dakota, just south of the Canada-United States border.

Enbridge said it was conducting final cleanup at the site and has sent the damaged pipe section to a metallurgical lab to help with the investigation into the cause of the rupture.