By Keith Coffman
DENVER, Dec 31 (Reuters) - The Federal Aviation Administration has launched an investigation into nighttime sightings of unidentified drones flying in formation over rural northeastern Colorado and southwest Nebraska over the last two weeks, the agency said on Tuesday.
The cluster of drones, technically known as unmanned aircraft systems, have been spotted in at least four counties in Colorado, garnering national media attention.
FAA spokesman Ian Gregor said in a statement emailed to Reuters that "multiple FAA divisions and government agencies are investigating these reports," adding that the agency does not comment on the details of its open investigations.
No private companies nor government agencies have claimed the drones.
The Phillips County, Colorado Sheriff's Office said in a Dec. 20 Facebook post it was investigating "multiple reports of drone sightings in the county over the last week."
On that day, deputies from Phillips and Yuma counties "tracked over 16 drones between the two counties. We believe that the drones, though startling, are not malicious in nature."
Phillips County Sheriff Thomas Elliot said in a phone interview that the drones with blinking lights are flying in square grid patterns nearly every night between 5 and 10 p.m., and appear to be widening their path.
"They now have moved into Morgan County (Colorado) and have been spotted in Perkins County, Nebraska," he said.
Elliot said he had spoken to FAA investigators about whether the agency could determine if the aircraft were being used to map the area for possible oil and gas exploration purposes.
Wyatt Harman, who chased the drones when they flew over his Washington County, Colorado, property, told NBC's Today show on Tuesday that seeing the mysterious aircraft was "unnerving."
"They can sit there and hover," Harman said. "They can descend very fast. They can take off very fast."
U.S. Senator Cory Gardner, a Colorado Republican and a member of the Senate Commerce Subcommittee on Aviation and Space, said in a Tuesday statement that he had been in contact with the FAA.
"I'm encouraged that they've opened a full investigation to learn the source and purpose of the drones," said Gardner, who is from Yuma County.
Last week, the FAA proposed requiring nearly all drones operating in U.S. airspace to be remotely tracked, a move which Sheriff Elliot said he would welcome.
"I could put all this to rest if whomever is doing this would come forward and identify themselves," Elliot said. (Additional reporting by David Shepardson in Washington; Editing by Bill Tarrant and Richard Chang)
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