Protests against the Dakota Access Pipeline in North Dakota turned violent on Saturday.

Demonstrators supporting the Standing Rock Sioux Tribe faced off with private security officers from Dallas-based Energy Transfer Partners.

Video from the scene showed security officers threatening protesters with dogs.

As All Things Considered reported, hundreds of Native Americans from tribes across the country have set up a camp near the construction site in North Dakota. The Army Corps of Engineer approved the oil pipeline in July allowing it to run under the Missouri river close to the Standing Rock Sioux Tribe's reservation.

Protesters worry that the $3.8 billion pipeline, which is slated to run through four states, could disturb sacred sites and affect the reservation's drinking water.

The show Democracy Now! was at the site of the protest on Saturday and documented some tense moments. Dogs appeared to bite protesters and security guards appeared to use pepper spray. Warning, the video below includes some fleeting expletives:

In a statement, the Morton County Sheriff's Department said protesters marched from their encampment onto private lands, where the pipeline is being constructed.

"Once protestors arrived at the construction area, they broke down a wire fence by stepping and jumping on it," the sheriff's office said. "According to numerous witnesses within five minutes the crowd of protestors, estimated to be a few hundred people became violent. They stampeded into the construction area with horses, dogs and vehicles."

Morton County Sheriff Kyle Kirchmeier said it "was more like a riot than a protest." Videos show some protesters were bloodied and the sheriff says three private security officers were hurt.

The AP adds the tribe is also challenging the pipeline in federal court. The AP reports:

"The protest Saturday came one day after the tribe filed court papers saying it found several sites of "significant cultural and historic value" along the path of the proposed pipeline."Tribal preservation officer Tim Mentz said in court documents that the tribe was only recently allowed to survey private land north of the Standing Rock Sioux reservation. Mentz said researchers found burials rock piles called cairns and other sites of historic significance to Native Americans."Copyright 2016 NPR. To see more, visit http://www.npr.org/.