At first, the white object in the sky looked like a cloud. A weather balloon, perhaps ?

The motionless, cigar-shaped object spotted last week near Fort Worth left the witness stumped. And a video of the sighting has since gone viral, opening the door to UFO theories online.

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"It was the oddest thing I've ever seen," the unidentified witness said, according to their report to Texas UFOs, a website that tracks mysterious UFO sightings throughout the state. "I watched it for about 20 minutes. It didn't move. I don't think I've ever seen anything in the sky stay that still before, not even for a few seconds, let alone 20 minutes."

RELATED: UFO enthusiasts say Houston has seen lots of strange flying objects in 2017

Several people commented on the YouTube video guessing it could be a blimp. However, a Texas UFOs administrator said they couldn't find any information the Goodyear blimp was scheduled to be in Keller on Nov. 18, the day of the sighting.

Further, the witness said it sat motionless in the sky for about 20 minutes, and similar UFO sightings were reported in Brownsville in August 2016 and El Paso in August 2018.

A few people went along for the ride on YouTube, with one commenter comparing the footage to "the classic cigar-shaped UFO" he saw in the mid 90's over Reading, Pennsylvania.

View the gallery to see other UFO sightings in Texas last year.

Julian Gill is a digital reporter in Houston. Read him on our breaking news site, Chron.com, and on our subscriber site, houstonchronicle.com. | julian.gill@chron.com | Text CHRON to 77453 to receive breaking news alerts by text message