A regulator says a man working on the four-state Dakota Access oil pipeline has been killed in an apparent accident in western North Dakota.

Public Service Commissioner Brian Kalk said Saturday that the man died of his injuries Friday afternoon. His name has not been released.

Kalk says the man was working as subcontractor for Dallas-based operator Energy Transfer Partners, which is building the nearly 1,200-mile pipeline from North Dakota to Illinois.

The pipeline in western North Dakota already is completed and is more than 200 miles away from a protest site in southern North Dakota.

Kalk says the man was on a tractor Thursday, covering the underground pipeline with soil and grass seed.

Kalk says the company reported the man suffered a serious head injury, apparently while working on equipment