(CNN)Cheers rang out at a protest camp in North Dakota on Sunday, as the Standing Rock Sioux tribe and its supporters learned that the US Army Corps of Engineers had blocked a measure to allow the construction of the Dakota Access Pipeline beneath Lake Oahe, a Missouri River reservoir.
Dakota Access Pipeline protesters rejoice: 'Prayers have been answered'
Tribe members and allies, including environmental activists and military veterans, had gathered at Standing Rock reservation since April, where they established camp and refused to leave until construction was halted.
Rallying under the banner "water is life," the protesters charged that the oil pipeline threatened the tribe's water supply and desecrated sacred lands. Many feared a pipeline leak could cause an environmental disaster.
The protests were largely peaceful, but at times devolved into chaos as law enforcement officers fired rubber bullets, tear gas and water at some activists who set fires, vandalized construction equipment and blocked building efforts.
Thousands of protesters were preparing to hold their ground through the cold winter when Jo-Ellen Darcy, the Army's assistant secretary for civil works, announced Energy Transfer Partners, the company constructing the pipeline, would have to re-route the $3.7 billion project.
The camp erupted in instant jubilation, with protesters cheering, crying tears of joy and beating drums.
"Prayers have been answered," Chief Arvol Looking Horse, Keeper of the White Buffalo Calf Pipe, told the protesters gathered at the camp. "I know that the great spirit is going to bless each and every one of you."
"People said we either make it or break it, and I guess we made it," he added.
Tribe members and supporters beat drums in celebration of their hard-fought victory against Dallas-based Energy Transfer Partners.
Chief Arvol Looking Horse of the of Lakota, Dakota, and Nakota Nation takes a moment to reflect on the protesters' great achievement.
A tribesman rides down from a snow-covered ridge overlooking Oceti Sakowin Camp on the edge of the Standing Rock Sioux Reservation.
A crowd cheers at Oceti Sakowin camp, elated that the tribe's water supply and sacred grounds remain safe.
Activists hold hands during a prayer circle that included Native-Americans and non-Native activists.
Protesters celebrate their great victory at Standing Rock Sioux Reservation.