600956838via: (theroot.com)  The Army Corps of Engineers announced Friday that the protesters fighting pipeline construction must vacate the property near the Cannonball River in North Dakota by December 5 or be taken into custody.

The order comes five days after a violent clash between protesters and local police at Standing Rock.

The clash resulted in a 21-year-old woman facing arm amputation after a concussion grenade thrown by police hit her in the arm.

The army corps says its recent action is based on the safety of protesters.

“This decision is necessary to protect the general public from the violent confrontation between protestors and law enforcement officials that have occurred in this area, and to prevent death, illness, or serious injury to inhabitants of encampments due to the harsh North Dakota winter conditions,” Col. John Henderson of the Corps said in a letter to the Standing Rock Sioux Tribe leader.

Tribal Chairman Cave Archambault II also issued a statement.

“Our Tribe is deeply disappointed in this decision by the United States, but our resolve to protect our water is stronger than ever,” he said. “The best way to protect people during the winter, and reduce the risk of conflict between water protectors and militarized police, is to deny the easement for the Oahe crossing, and deny it now.”

Protesters say the pipeline will threaten the environment and destroy Native American burial sites, prayer sites and culturally significant artifacts as well as poison the water supply.

Archambault urged the public to ask President Obama and the Corps to change the pipeline route.

“It is both unfortunate and disrespectful that this announcement comes the day after this country celebrates Thanksgiving—a historic exchange of goodwill between Native Americans and the first immigrants from Europe,” he wrote. “Although the news is saddening, it is not at all surprising given the last 500 years of the mistreatment of our people.”

On Black Friday, more than 33 anti-pipeline protesters were arrested and charged with criminal trespass after about 100 of them formed a prayer circle inside a Bismark mall, police said. CNN reports that more than 500 #NoDAPL protesters have been arrested all over the country in the last month.