Protesters clashed with law enforcement officials near the site of the Dakota Access Pipeline, with at least one person arrested as protesters sought to push past a bridge on a state highway that had been blockaded since late October.

The Morton County Sheriff’s Office estimated that 400 protesters were trying to cross the bridge on state highway 1806 in what they called “an ongoing riot”. 

The Backwater Bridge has been closed since late October, when activists clashed with police in riot gear and set two trucks on fire, prompting authorities to forcibly shut down a protesters encampment nearby.

The $3.7bn Dakota Access project has been drawing steady opposition from Native American and environmental activists since the summer.