Native American leaders have vowed to protest against a proposed pipeline in North Dakota through the Winter months.
A group of around 200 Native American demonstrators have also returned to the scene where an earlier confrontation with police took place.
They staged a peaceful ceremonial prayer vigil near the town of Cannon Ball, at the edge of the Standing River Sioux Reservation.
Tensions have been high in recent days between protesters and law enforcement over the planned oil pipeline.
According to reports, at least 10 shelters have been readied on tribal land against temperatures which can turn as low as -37 Celsius for days at a time.
The planned 1,172-mile (1,885-km) path of the pipeline, the project of a group of companies led by Energy Transfer Partners LP, would skirt the Standing Rock reservation by about a half mile.
But the Standing Rock tribe and environmental activists say it threatens water supplies as well as sacred Native American sites.