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Dec 6 (Reuters) - A crude oil transmission line was shut down in western North Dakota following a leak that spilled oil into a creek, the state said on Tuesday.
The size of Monday's leak and extent of the spill were not yet known. It occurred as Native Americans, climate activists and other protesters were camped around 200 miles away at the Dakota Access pipeline project site over concerns a leak there could contaminate the water supply.
The leak that prompted the shutdown was discovered in a six-inch pipeline operated by Belle Fourche Pipeline Company, the North Dakota Department of Health said. An undetermined amount of crude oil was spilled, the state said.
"A series of booms have been placed across the creek to prevent downstream migration and a siphon dam has been constructed four miles downstream of the release point," Bill Suess, spill investigation program manager for the North Dakota Department of health, said.
The spill leaked oil into the Ash Coulee Creek in Billings County.
Since 2011, the Belle Fourche Pipeline has had 10 reported spills, totaling 4,848 barrels and $2.26 million in property damage, according to the U.S. Department of Transportation's Pipeline and Hazardous Material Safety Administration (PHMSA).
The federal agency has also issued six warning letters to the pipeline company regarding integrity issues and safety procedures.
PHMSA has been notified of the incident, an agency spokeswoman said.
Belle Fourche Pipeline is a 783-mile liquids pipeline. The company transports crude oil in the Williston Basin of western North Dakota and eastern Montana, and the Powder River Basin of Wyoming, according to the company website.
The Dakota Access Pipeline, owned by Texas-based Energy Transfer Partners LP, had been completed except for a segment planned to run under Lake Oahe, a reservoir formed by a dam on the Missouri River.
Reporting by Nithin Prasad in Bengaluru and Jarrett Renshaw; Editing by Jim Finkle, David Gaffen and Meredith Mazzilli