Residents in northeastern Colorado and southwestern Nebraska have been confused for weeks after a series of unexplained night-time sightings of drones which has drawn attention from the FBI, the Federal Aviation Administration (FAA) and the US military.
“There is no local crime that I am aware of that has been committed, but it is very unnerving for our citizens,” Morgan County Sheriff Dave Martin told the state’s public radio network.
“Everybody's concerned because of the unknown. A lot of our sheriff and law enforcement partners have been busy with these types of calls trying to figure out what it is and who it is.”
The drones, which were first seen in December, have been described as having 2-metre wingspans and reportedly fly in a grid-like pattern in groups of six to 10.
In a statement on Monday, the FAA said it takes “every drone-sighting report seriously”.
“Multiple FAA divisions are working closely with federal, state and local stakeholders to try to determine whether the reported sightings in Colorado and Nebraska are drones and, if so, who is operating them and for what reason,” the organisation said.
After a strategy meeting with federal, state and local law enforcement agencies, Phillips County Sheriff's Office said that it is looking for a command vehicle for the drones.
The sheriff’s office added that none of the agencies could confirm if the drones were malicious, although they do not believe the aircraft were intended to harm people.
“They’ve got two red blinking lights and a white light,” Deanna Schwindt, a resident from the town of Brush, told Colorado Public Radio.
“You just see the lights coming, coming from the east. It's weird.”
Ms Schwindt said she had seen drones flying over her house every night for about a week, starting at about 5pm each night.
Colorado’s The Gazette has suggested the drones could be connected to a secretive Air Force programme intended to keep eyes away from nuclear missile silos.
Air Force Global Strike Command has confirmed it conducts counter-drone operations out of the F E Warren Air Force Base in Cheyenne, Wyoming, near where the drones have been seen.
However, the Air Force has denied ownership of the aircraft.
“They’re not from F E Warren and they are not part of our counter-drone system,” Lt Jon Carkhuff, a spokesperson for the base, told The Denver Post.
“We do not know where they are coming from, but we are cooperating with the FAA and the FBI and numerous police departments to find out what those sightings are.”
The Drug Enforcement Administration (DEA) has also said it does not have any information on the drones.
All of the agencies contacted by the newspaper have denied ownership.
Last month, the FAA proposed a new rule which would require drones to be registered with remote identification technology so agencies can track aircraft flying in their jurisdiction.
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