According to the sheriff's department, the bullets were used on one person throwing bottles at officers and another who charged police and refused to show his hands. Tear gas was also used on protesters.

Brunner and one other protester said they had no intent to stop pipeline construction Wednesday, as a sheriff's department spokeswoman said earlier in the day. She said there are burial sites where the police were staged on the bluffs above the creek.

"All we were trying to do is build a bridge across so we can pray," Brunner said.

However, a protest organizer said part of the reason for building the bridge was that North Dakota Highway 1806, the northern route from camp, has been closed since Oct. 27, when several vehicles were burned on the Backwater Bridge following a daylong confrontation.

"We've got to make some access to get up and protect those sites," said Camp-Horinek.

In a Tuesday letter from the corps to the sheriff's department, Cpl. John Henderson said protesters began on Monday using small boats to travel up the creek and camp on corps land where the pipeline is to be drilled under the Missouri River.