CANNON BALL, N.D. (AP) — Authorities are defending their use of water hoses against Dakota Access oil pipeline protesters during a skirmish in below-freezing weather.

Morton County Sheriff's spokesman Rob Keller says the water hoses were used to put out fires set by protesters and to keep protesters away from law officers during a violent clash that was "rapidly unfolding."

The conflict between protesters and officers happened late Sunday and early Monday on a long-blocked bridge on state Highway 1806, near a camp where demonstrators have gathered for months.

Dallas Goldtooth with the Indigenous Environmental Network says at least 17 people were taken to hospitals, some with hypothermia.

Authorities say protesters assaulted officers with rocks and burning logs, and one officer was injured. One protester was arrested.

Tension flared over the weekend anew on the Dakota Access pipeline as protesters tried to push past a long-blocked bridge on a state highway, only to be turned back by a line of law enforcement using water cannon and what appeared to be tear gas.

Sunday's skirmishes began around 6 p.m. after protesters removed a burned-out truck on what's known as the Backwater Bridge, not far from the encampment where they've been for weeks as they demonstrate against the pipeline. The Morton County Sheriff's Department estimated 400 protesters sought to cross the bridge on state Highway 1806.

At least one person was arrested.

Protesters said a gym in Cannon Ball was opened to aid demonstrators who were soaked on a night the temperature dipped into the low 20s or were hit with tear gas.