(CBS4) – There’s a mystery unfolding on Colorado’s Eastern Plains. Massive drones have been spotted flying over towns but no one seems to know where they are coming from.

(credit: CBS)

The following counties have all launched investigations: Morgan County, Yuma County, Logan County, Washington County, Phillips County and Weld County.

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The drones reportedly have 6 foot wingspans, which makes investigators think they don’t belong to a hobbyist. Phillips County Sheriff Thomas Elliot told the news agency Reuters that in addition to Colorado sightings there have been some in Nebraska.

So far the military and government agencies deny that the drones belong to them.

The FAA says it is looking into the mystery.

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Sen. Cory Gardner, Colorado’s junior senator, tweeted about the situation on Tuesday, writing “I’ve been in contact with the FAA regarding the heavy drone activity in Eastern Colorado and I’m encouraged that they’ve opened a full investigation to learn the source and purpose of the drones. I will continue to closely monitor the situation.”