Tensions over the Dakota Access oil pipeline flared again Sunday when North Dakota law enforcement used water cannons to disperse a group of about 400 protesters trying to move past a barricaded bridge toward construction sites for the project. As temperatures in Cannon Ball, N.D., dropped into the 20s, police in riot gear sprayed activists with a hose mounted atop an armored vehicle...according to the Bismarck Tribune... A grainy Facebook Live video from the scene shows...a haze of smoke and water vapor rising near police vehicles.

...[P]rotesters tried to remove burned-out trucks that had been blocking the bridge... Police have [also]...set up wire and concrete barriers on the bridge, which is about a mile south of where the pipeline developer plans to drill. Protesters, who call themselves “water protectors,” have argued that the barricade prevents emergency services from reaching the Standing Rock Sioux Reservation and a nearby camp they have used as a staging ground for demonstrations...

The Morton County Sheriff’s Department said that by 8:30 p.m., an estimated 400 people had arrived to try to “breach” the bridge and had set dozens of fires in the area. The department called the situation an “ongoing riot”... One of the protest organizers, Dallas Goldtooth, said protesters started small fires in the area to help warm people who had been sprayed with water in the freezing cold...

...Physicians and tribal healers with the Standing Rock Medic and Healer Council called on authorities to stop using water cannons against the protesters, saying the below-freezing weather could cause hypothermia and criticizing the “potentially lethal use of these controversial methods against people peacefully assembled,” CNN reported... The Standing Rock Sioux argue that the pipeline...could pollute water and disrupt cultural sites... Energy Transfer Partners...says the pipeline transports oil more safely than trucks and will not harm sacred lands.