A groundswell of Native American activists has temporarily shut down construction on a major new oil pipeline with an ongoing protest that has drawn around 1,200 people to Cannon Ball, N.D.

Construction workers walked away from their bulldozers Monday after protesters surrounded the equipment and called for an end to construction of the Dakota Access pipeline. A group of protesters on horseback also staged a mock charge toward a line of law enforcement officials guarding the site, and the county sheriff alleged others have fired guns and set off pipe bombs.

The $3.8 billion pipeline at the heart of the protest would carry about half a million barrels of crude oil per day from the Bakken oil field to Illinois where it would link with other pipelines to transport the oil to Gulf Coast refineries and terminals.

The protest was staged at a spot where the pipeline would pass beneath the Missouri River, just upstream from the Standing Rock Sioux reservation, a community of 8,500 along the Missouri River in North and South Dakota.  

Protesters from dozens of tribes across the country are now camping in tents, tepees and mobile homes at the Sacred Stone Camp a mile and a half from the construction site. A video shows a second, more recently established campsite, the Red Warrior Camp.