A protest of a four-state, $3.8 billion oil pipeline turned violent after tribal officials say construction crews destroyed American Indian burial and cultural sites on private land in southern North Dakota.

Morton County Sheriff’s Office spokeswoman Donnell Preskey said four private security guards and two guard dogs were injured after several hundred protesters confronted construction crews Saturday afternoon at the Dakota Access pipeline construction site just outside the Standing Rock Sioux reservation... 

Tribe spokesman Steve Sitting Bear said protesters reported that six people had been bitten by security dogs, including a young child. At least 30 people were pepper-sprayed, he said. Preskey said law enforcement authorities had no reports of protesters being injured.  There were no law enforcement personnel at the site when the incident occurred, Preskey said...

Vicki Granado, a spokeswoman for Dallas-based Energy Transfer Partners, which is developing the pipeline, said the protesters broke through a fence and “attacked” the workers... Morton County Sheriff Kyle Kirchmeier said in a statement that “individuals crossed onto private property and accosted private security officers with wooden posts and flag poles.”