The federal government is investigating the appearance of a mystery object spotted by a pilot in the skies over Denver Monday.

Updated at 3:30 p.m. ET: The Federal Aviation Administration emailed USA TODAY with the following statement regarding the object: " The FAA is investigating the incident and will try to positively identify the object the Citation pilot reported, where it came from and who was operating it."

Original post: A mystery object that flew over Denver Monday evening is raising questions and prompted the Federal Aviation Administration to investigate, 9 News out of Denver reports.

The mystery object turned up when a Cessna corporate jet was flying at 8,000 feet above sea level, the news organization reports. At that point, recordings indicate, the pilot radioed to air-traffic control in a shaky voice: "A remote-controlled aircraft, or what? Something just went by the other way ... about 20 to 30 seconds ago. It was like a large remote-controlled aircraft."

Greg Feith, the station's aviation analyst and a former National Transportation Safety Board investigator, has some thoughts on what the object might have been:

a military or law enforcement drone

a remote-controlled aircraft

a large bird

"That's an issue because now we have something in controlled airspace that poses a danger," the station quoted Feith as saying.

The FAA plans to talk to the pilot and examine other clues, according to 9 News.

"The threat is there from a collision standpoint," agency spokesman Mike Fergus told the station. "We'll do as much as we can here to try to track down what time it was, probably talk with some remote-control clubs, that kind of thing."