A year-long protest against an oil pipeline in North Dakota appears to be nearing its end, although some remain in defiance at a deadline to leave.
Some demonstrators who ignored requests to depart were arrested, and makeshift wooden structures were set ablaze.
A boy aged seven and a girl, 17, are being treated for burns following two explosions resulting from the fires.
A federal judge has rejected a request by two Native American tribes for an emergency order blocking the pipeline.
The two tribes say the $US3.7 billion pipeline creates a risk of water pollution and endangers sites they consider sacred.
The protest camp was located on federal land near the Standing Rock Sioux Reservation.
US President Donald Trump has signed an executive order authorising the Dakota Access Pipeline to proceed, arguing it will bring huge economic benefits.
When completed, by Dallas-based Energy Transfer Partners, the project will take oil through the Dakotas and Iowa to Illinois to be shipped.
Earlier on Wednesday, about 150 people departed the camp for the last time as a deadline to leave the area approached.
Up to 75 people remained outside the camp and at least nine people were taken into custody for failing to leave, authorities said.
Lt Tom Iverson said police would not enter the camp on Wednesday night.
At its peak in the autumn, the protest camp had thousands of people, but that has fallen to a couple of hundred in the last few weeks.