SUPERIOR, Wis. — Protesters opposing the replacement of Enbridge Energy’s aging Line 3 oil pipeline shut down construction in northern Wisconsin for a brief time.

Enbridge spokeswoman Jennifer Smith says a group of about 20 protesters entered a worksite outside Superior on Monday and vandalized equipment before leaving on their own. She didn’t immediately have a damage estimate.

Video footage posted on social media shows masked protesters locking themselves onto equipment.

Smith says there were no injuries and no arrests. Douglas County Sheriff Tom Dalbec didn’t immediately respond to a request for comment.

The Line 3 pipeline carries Canadian crude from Alberta to Wisconsin, clipping the northeastern corner of North Dakota and crossing northern Minnesota. Enbridge is working to replace the line but tribal and environmental groups are fighting the $7.5 billion project.