The strange lights began appearing in the night sky a week before Christmas.

A formation of unidentified drones, some in groups of 30, have been reported flying high above a corner of rural northeastern Colorado and western Nebraska, usually between 7 and 10 p.m. By some accounts, the drones have wingspans of 6 feet or more.

"They can sit there and hover. They can descend very fast. They can take off very fast," Wyatt Harman, who chased the drones as they flew above his land in Washington County, Colorado, told the "TODAY" show.

He and his girlfriend, Chelsea Arnold, said they pursued the lights for about 15 miles, driving as fast as 70 mph.

"It's more unnerving than anything," Arnold said.

But the couple came no closer to figuring out who or what could be behind the squadron of drones. Still, the theories abound, with some people speculating that private companies could be using the aerial robots to survey for oil or natural gas or someone's doing practice runs for drone shows at sporting events or theme parks.

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