Clashes between protesters and authorities over the Dakota Access Pipeline escalated Sunday night after an estimated 400 people tried to breach a law enforcement barrier, North Dakota law enforcement officials said.
The Morton County Sheriff's Office described the clash as a "riot" prompted by "very aggressive" activists, while protesters said authorities used tear gas, rubber bullets and water cannon in below-freezing temperatures.
NBC News couldn't independently confirm the use of rubber bullets, and a sheriff's spokesman, Rob Keller, told NBC News that no water cannon were deployed. He said the water was being sprayed from a fire truck to control blazes as they are being set by activists.
Atsa E'sha Hoferer of the Walker River Paiute Tribe, who called himself a "water protector," said he was hit with tear-gas and sprayed with water. Hoferer said demonstrators were lighting fires to provide warmth in the 25-degree weather.
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"They're saying that we're causing multiple fires out here, but we're really only using them to stay warm," said Hoferer, 27. "I'm just a father with a phone that loves his water, that wants his water to be clean for his children and grandchildren."
In a statement, the sheriff's office acknowledged that tear gas and other "less than lethal means" were being used after protesters "engaged in organized tactical movement and attempted to flank and attack" a law enforcement line near a bridge.
The bridge had been closed since late October, when it was damaged in a fire after authorities evicted protesters from property owned by the pipeline developer.