He said law enforcement isn’t privy to where actions are planned and depends on tips from the public, landowners and pipeline operators and direct calls for assistance.

Last week, law enforcement swapped in the National Guard to man a Highway 1806 checkpoint en route to the reservation in order to put more patrol officers in the rural Morton County area.

Until now, the six-week stand against the Dakota Access Pipeline had been primarily centered near the Standing Rock Sioux Reservation. Tribal members and others occupying a large encampment of about 2,000 people have focused on stopping the pipeline from crossing the river for fear it will contaminate the water and harm what they call sacred lands just north of the reservation boundary. For now, construction is officially stopped at the crossing by order of the U.S. Army Corps of Engineers while it examines the tribe’s claims and past reviews.

Cody Hall, a leader of the Red Warrior Camp who Monday pleaded not guilty to misdemeanor trespass charges from earlier actions, said the actions further up the pipeline are intended to “prevent it from being built.”