The Federal Aviation Administration is working with state and local authorities to determine who’s behind a series of mysterious nighttime drone flights over northeastern Colorado and western Nebraska. A few sightings have also come from northwest Kansas, close to the Nebraska border.

A Colorado sheriff hosted a meeting with law enforcement agencies and government officials Monday to talk about the recent rural sightings. The drones reportedly have 6-foot wingspans and fly in grid-like patterns hundreds of feet in the air in groups of six to 10.

(Read more: KFDI 101.3)