Authorities in North Dakota plan to block supplies from reaching pipeline protesters, in order to force the demonstrators to leave the site, law enforcement officials said on Tuesday. For months, activists have protested plans to build the Dakota Access Pipeline—a $3.8 billion project—beneath a lake near the Standing Rock Sioux tribe. Maxine Herr, a spokeswoman from the Morton County Sheriff's Department, said building materials and food will be blocked from entering the camp. Governor Jack Dalrymple reportedly signed an "emergency evacuation" order on Monday to that same effect. Protesters allege the project will pose a threat to water resources and to the integrity of sacred Native American sites.