A woman who may lose her arm from an injury she sustained this week during a Dakota Access Pipeline protest was hit by a police concussion grenade, according to two people who say they witnessed the clash.

The witnesses, whose accounts were reported by the Montana Standard on Wednesday, contradict North Dakota sheriff’s department statements that said Sophia Wilansky, 21, was likely hurt by protesters mishandling a homemade explosive.

Wilansky stood near a barricade opposite law enforcement officials on a bridge early Monday after police had doused protesters with a water canon in sub-freezing temperatures, the newspaper reported.

“The girl (Wilansky) got hit by a rubber bullet and she fell,” Alonzo Willis, 23, told the Montana Standard. “And then they shot a percussion grenade and it got her in the arm.

“It hit her and it just went, ‘Boom!’ It blew her down,” Willis said.

Willis’ friend, Isaiah Other Bull, gave a similar account to the newspaper. Their stories echo accounts that circulated online with graphic photos of Wilansky’s injury.

Wilansky saw an officer throw the stun grenade at her, her father said Tuesday outside the Minneapolis hospital where his daughter faces numerous surgeries aimed at saving her limb.

The Morton County Sheriff’s Department, which has been accused of civil rights violations by a Native American tribe protesting the pipeline, blamed reckless activists for the blast.

“Law enforcement witnessed protesters rolling cylinders on the bridge and witnessed an explosion, shortly after they saw several protesters run to that area of the bridge and carried a woman off the bridge.,” the sheriff’s department said in a Facebook post.

The post included photos of what the department said were improvised explosives found “once the scene cleared.”

The state highway patrol denied that officers deployed anything powerful against the protesters. Wilansky’s injuries “are inconsistent with any resources utilized by law enforcement and are not a direct result of any tools or weapons used by law enforcement,” a North Dakota Highway Patrol spokesman said.

Conflict between law enforcement and pipeline opponents, sometimes numbering in the thousands, have grown frequent. More than 500 protesters, who generally prefer to be called water protectors, have been arrested by the Morton County Sheriff’s Office.

The Standing Rock Sioux tribe and their supporters oppose a stretch of the 1,172-mile pipeline that would cross beneath the Missouri River in North Dakota because of its proximity to the tribe’s reservation and water source. They also claim the project violates an 1851 federal treaty.

The project’s future is in limbo. The Obama administration has withheld a permit to pipeline owner Energy Transfer Partners that would allow construction of the disputed stretch near the site of most protests. Officials are reviewing whether initial approval by the Army Corps of Engineers was proper.

The pipeline would carry 570,000 barrels of crude from the Bakken oil fields in North Dakota to Illinois. Energy Transfer Partners has said pipelines are far safer than moving oil by truck or train. CEO Kelcy Warren has disputed that construction has desecrated tribal burial grounds and refuses to alter the planned route.

Warren also has expressed hope that President-elect Donald Trump will give permission to finish the project.