Authorities in North Dakota have arrested a dozen people protesting the $3.8 billion Dakota Access Pipeline.

Morton County Sheriff Kyle Kirchmeier said the 12 arrests as of Thursday evening were for disorderly conduct or criminal trespass.

He says some protesters encroached on a zone established for workers' safety. Those arrested were brought to the Morton County Correctional Center.

The pipeline would start in North Dakota and pass through South Dakota and Iowa before ending in Illinois.

Native Americans have been staging a nonviolent protest for months at a "spirit camp" established by the Standing Rock Sioux at the confluence of the Cannonball and Missouri rivers. The tribe has sued federal regulators for approving the pipeline.

Tribal member LaDonna Brave Bull Allard says roughly 200 people are protesting.