Dozens of people were arrested Saturday while protesting the Dakota Access Pipeline.
The Morton County Sheriff's Office posted to Facebook that that as of 5 p.m., 83 protesters had been arrested.
Officials say a group of about 300 activists marched onto a private construction site in North Dakota.
Law enforcement found some protesters had slashed the tires of a vehicle and attached themselves to it, the Forum says.
“Today’s situation clearly illustrates what we have been saying for weeks, that this protest is not peaceful or lawful," Sheriff Kyle Kirchmeier said in a statement.
The sheriff went on to say the protesters "engaged in escalated unlawful tactics" during the rally.
"This protest was intentionally coordinated and planned by agitators with the specific intent to engage in illegal activities," Kirchmeier said.
According to the Washington Times, officers used pepper spray against activists when some tried to break a police line. Then at one point, a protester grabbed a can and sprayed an officer in the face.
The Forum says that since August, more than 160 people have been arrested for protesting the pipeline.
In September, the court ordered work within 20 miles of Lake Oahe be temporarily halted while they figured out if work should be permanently shut down, Bloomberg reported. That decision came after the Standing Rock Sioux Tribe asked for an emergency injunction, claiming the work would damage sacred land.
Then earlier this month, a court issued a final verdict on the controversial project. It said the tribe didn’t provide enough persuasive proof for the court to stop things.
However, various groups issued a joint statement saying they’re still not ready to give the full go-ahead for construction work to start on any federal land along the route.
The protests have been called the largest Native American gathering in over 100 years. Thousands of people have joined in the protests, which turned violent at one point when a private security company came on site to try and stop the protesters. Other cities, including St. Paul, have held rallies in solidarity.