Gov. Jared Polis and other officials are monitoring the appearance of drones in northeastern Colorado, more than one week after The Denver Post first reported on the sightings.

“I’m actively monitoring the reports of drone sightings in eastern Colorado and share the expressed concerns of law enforcement and local residents,” Polis said, according to The Post.

Authorities in Philips and Yuma counties have reported that the drones typically fly in groups, and the Federal Aviation Administration has no information about who is operating them. A handful of government agencies and the University of Colorado have all denied that they are responsible.

On Tuesday, U.S. Sen. Cory Gardner, who is from Yuma, released a statement that he has been in contact with the FAA on this issue.

“I’m encouraged that they’ve opened a full investigation to learn the source and purpose of the drones,” he said.

A map of drone sightings indicates that they have appeared almost as far east as Lincoln, Neb., and as close to the Front Range as Roggen.

One user on the NightDrones.net forum posted on Wednesday that “We need to put a call out for people to be out looking earlier tomorrow so we can catch them in transit that will help us get a direction they are coming from. Ideally people should be encouraged to post time of sighting, number of drones, city and nearest cross streets.”