A crude oil pipeline in western North Dakota has been shut down following a leak that spilled oil into a creek, state officials reported 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 camped about 200 miles away, at the site of the controversial Dakota Access pipeline project over concerns a leak there could contaminate the water supply.

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The leak that prompted the shutdown was discovered in a six-inch pipeline operated by Belle Fourche Pipeline Co., 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 4 miles downstream of the release point," Bill Suess, spill investigation program manager for the North Dakota Department of Health, said Tuesday.

This spill apparently has leaked oil into Ash Coulee Creek in Billings County.

Since 2011, Belle Fourche Pipeline Co. 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 about the latest incident, an agency spokeswoman said.

Belle Fourche Pipeline Co. is a liquids pipeline operator that 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's website.

The Dakota Access Pipeline, owned by Texas-based Energy Transfer Partners LP, is complete except for a segment planned to run under Lake Oahe, a reservoir formed by a dam on the Missouri River. The U.S. Army Corps of Engineers has denied an easement for the pipeline to pass under Lake Oahe.