Police officials in North Dakota are calling in the reserves, while looking to maintain order during a sustained protest involving the $3.7 billion Dakota Access Pipeline.

The pipeline, which is to be constructed near the reservation of the Standing Rock Sioux tribe, has become the target of a large encampment of protesters, many of whom hail from out of state. Protestors object that the pipeline could harm the local water supply and disturb tribal burial sites.

Policing the protest has strained local law enforcement resources, which is why two separate associations—the Western States Sheriffs’ Association (WSSA) and the National Sheriffs’ Association (NSA)—have pledged to supply support for officers in Morton County.

So far, much of the help the officers have received has come from inside North Dakota. The two associations will help bring in officers from around the country.

Sheriff Danny Glick, president of WSSA and a past president of NSA, reached out to Kyle Kirchmeier, sheriff of Morton County, pledging assistance. “When we get a call from Sheriff Kirchmeier, we will be ready to respond and assist where we are able,” said Glick, the sheriff of Laramie County, Wyoming, in a press conference covered by Prairie Public News.

This week, protesters said they wouldn’t leave the location anytime soon, and the protest has drawn interest from increasingly prominent activists. This week, actress Shailene Woodley was arrested while taking part in a peaceful protest, as was a local politician in Madison, Wisconsin.

Despite the protest, a court decision over the weekend allowed workers to restart construction on the pipeline.

Dakota Access Pipeline protesters square off against police near the Standing Rock Reservation. (Terray Sylvester/Reuters)