Residents of northeast Colorado should not attempt to shoot down the drones flying over Yuma and Phillips counties, even though the owner of the drones is a mystery.

The Denver Post reports that for the past week, drones flying in an apparent grid search pattern are not the property of the Federal Aviation Administration, the Drug Enforcement Administration or the U.S. Air Force. The Phillips County sheriff’s office said that it is unlikely that the drones are the property of hobbyists.

Shooting down the drones is a federal crime, and the battery within the device could also spark a fire.

In Jan. 2018, the Flight Safety Foundation reported that the FAA received registrations for one million drones total, nearly 88% of which were hobbyist-owned. Originally, a 2015 law required that drones between 0.55 and 55 pounds be registered.

The Associated Press reported in 2015 that the Federal Bureau of Investigation was using drones registered through front companies to conduct video and cellphone surveillance in more than 30 cities.

The drones in northeast Colorado reportedly fly too high to be audible from ground level and reached speeds in excess of 50 miles per hour.

“They do not seem to be malicious,” Phillips County Sheriff Thomas Elliott told The Post.