The North Dakota Army National Guard has deployed two surface-to-air missile-launchers near a critical work site for the controversial Dakota Access Pipeline, or DAPL.

Protestors spotted one of the Avenger missile systems on Jan. 16 and posted photos and videos on Facebook. “Anti-drone missile system confirmed on top of a hill guarding the DAPL drill pad,” Jon Ziegler, a self-described “citizen journalist,” wrote on Facebook.

North Dakota Guard spokesman William Prokopyk told The Daily Beast that the Avenger’s missile tubes aren’t loaded. “These systems have observation capabilities and are used strictly in the observation role to protect private property and public safety,” Prokopyk said.

“There’s no authority to arm them,” he stressed, adding that the two Avengers have been in Morton County—site of the drill pad—for more than a month without incident.

The drill pad the Avenger is “protecting” belongs to Dakota Access, LLC, the company building the nearly 1,200-mile-long pipeline meant to transport oil from North Dakota’s Bakken oil field to a storage facility in Illinois.

Dakota Access had hoped to extend the pipe underneath Lake Oahe, which lies on federal land in southern North Dakota. A protest movement originating with the Standing Rock Indian Reservation, which lies on Oahe’s western shore, successfully pressured the Obama administration to deny Dakota Access the easement it needed to drill underneath the lake.

But Dakota Access has vowed to complete the $4-billion pipeline, apparently via an alternate route. Work continues on private land. And it’s on this land that the Guard has stationed its missile launcher.

The Morton County Sheriff’s Department commented on the Avenger deployment on Facebook shortly after The Daily Beast began making inquiries. “MYTH: Law enforcement has [an] anti-drone missile system on the top of a hill to guard the DAPL drill pad and shoot down drones,” the department wrote.

“FACT: The N.D. National Guard does have an Avenger system employed in support of the Dakota Access Pipeline Protest,” the department continued. “These systems are used strictly for observation of ungoverned encampments to help protect private property and maintain public safety.”

Still, the presence of a missile launcher—even an unloaded one—will likely increase tensions between the Standing Rock protestors and authorities. Police in North Dakota have come under scrutiny for using violent, military-style tactics against peaceful, unarmed protestors.

The Avenger is foremost a weapon of war. It combines a Humvee truck chassis with a rotating turret that can be armed with eight Stinger missiles and a .50-caliber machine gun. The North Dakota Army National Guard’s 1st battalion, 188th Air Defense Regiment—which has companies in Bismark, Fargo and Grand Forks—operates Avengers.

When fully armed, the Avenger can engage airplanes, helicopters—and, yes, drones. On Oct. 23, 2016, the Morton County Sheriff’s Department announced it had shot down a protestor’s drone after it had approached a police helicopter “in a threatening manner.”

The drone’s operator denied endangering any aircraft. Nevertheless, the FAA subsequently established a no-fly-zone over the pipeline work site.

Prokopyk said the Guard sent the Avenger because it possesses night-vision equipment that many North Dakota Guard units lack, and because the Avenger has an enclosed, heated crew compartment. “With wind chill here, it’s been negative 45 degrees,” Prokopyk said. “I’m not kidding.”

Prokopyk declined to say whether the Avenger crew at the drill pad is using the vehicle’s night-vision equipment specifically to detect activists’ drones.

Around 200 “water-protectors” from the main Standing Rock protest camp reportedly cut through a fence and attempted to reach the drill pad on Jan. 16. Police and National Guardsmen stopped the protesters from reaching the pad. But the activists got close enough to spot an Avenger.

“Many water protectors made it further around the bend to the east closer to the drill site and were met with police and reports of mace used,” Ziegler wrote on Facebook. “We climbed up the hill on the west side right up next to the launcher.”

The Morton County Sheriff’s Office said three people were arrested during the Jan. 16 protest.