Hundreds of clergy of various faiths have joined protests against the Dakota Access oil pipeline in southern North Dakota.

The Unitarian Universalist Association says the goal of the event is to draw attention to the concerns of the Standing Rock Sioux and push elected officials to call for a halt to construction. The tribe says the $3.8 billion four-state pipeline threatens its drinking water and cultural sites.

Clergy and protesters gathered at a campfire at the main protest camp to burn a copy of a religious document from the 1400s that attempted to justify the taking of land from indigenous peoples. Hundreds then sang songs while they marched to a bridge that was the site of a recent clash between protesters and officers.

Officers monitored Thursday's ceremony but didn't intervene.