A quiet canyon in Utah’s Red Rock country has sent the world’s imagination into overdrive.

Members of the Utah Department of Public Safety’s Aero Bureau were assisting Wildlife Resources in a routine count of bighorn sheep on Nov. 18 when they spotted the monolith — a tall, metallic reflective structure that clearly had been placed there.

But the question was: by whom?

The Public Safety Department admitted that it didn’t know who — or what — installed the monolith, and it wouldn’t even tell the public where, exactly, in the large and remote southeastern corner of the state the structure stood.

The public’s first guess: aliens, of course. Theories and jokes abounded. Ones that only grew stronger after the federal Bureau of Land Management said Saturday that the monolith had suddenly disappeared. In its place was a pile of rocks, appearing to commemorate the vanished structure.

#WhereDidItComeFrom #WhereDidItGo,” the San Juan County Sheriff’s Office wrote on Facebook.

Pilot Bret Hutchings said that when one of his officers spotted the monolith, it felt like a scene right out of the Stanley Kubrick classic “2001: A Space Odyssey.”

“He was like, ‘Whoa, whoa, whoa, turn around, turn around!’ And I was like, ‘What?’ And he’s like, ‘There’s this thing back there — we’ve got to go look at it!'” Hutchings told NBC affiliate KSL of Salt Lake City. “We just happened to fly directly over the top of it.”

Immediately, people started making alien jokes, and when the monolith disappeared, the jokes didn’t.

Right now an alien is asking his friends if they’ve seen his charger. https://t.co/o1UaHvTkXs

— NoelCaslerComedy (@CaslerNoel)

Some alien needs to tile their damn keys https://t.co/Gc3UQOfsnO

— PJ Vogt (@PJVogt)

You know in the horror movie where the big scary thing that’s about to happen is just playing in the background on the news for the first 15 minutes? That’s how I feel about the Utah desert monolith.

— Jesse McLaren (@McJesse)

The alien gag become so popular that CNN even ran a headline saying, “The Utah monolith probably wasn’t the work of aliens,” implying a small chance that extraterrestrials gad, indeed, placed it there.

Sorry y’all, we needed it back. https://t.co/tuOKj1igF7 pic.twitter.com/d3SOF4GeMS

— Southwest Airlines (@SouthwestAir)

And in its post about the disappearance, the sheriff’s department poked fun at the alien theories, posting a collage of aliens from movies on Facebook and asking residents whether “you recognize anyone from the lineup provided as being in the area of the strange structure on the night of November 27th.”

But while the monolith was still in the canyon, a more plausible theory was developing.

Hutchings, the pilot, acknowledged that the silver monolith appeared to be some sort of “new wave” art installation, and quickly, people began to wonder which one.

One theory posited that the monolith was a work by Petecia Le Fawnhawk, a Southwestern artist who used to live and work in Utah. Le Fawnhawk has previously installed sculptures in the desert, but she told Artnet News that while she “did have the thought to plant secret monuments in the desert,” she “cannot claim this one.”

Others, including The Art Newspaper, said it immediately scanned the monolith as the work of the sculpture artist John McCracken, who died in 2011 and lived in New Mexico.

David Zwirner, whose gallery represented McCracken and showed his work, originally said he believed the structure to be McCracken’s, but has since changed his mind.

“I love the idea of this being John’s work, but when you look closely at the photos of the Utah monolith, you will see rivets and screws that are not consistent with how John wanted his work to be constructed,” Zwirner said in a statement. “He was a perfectionist. While I know that this is not John’s work, I also know that he would have enjoyed the Utah location and would have greatly appreciated the mystery surrounding this work. We all think it is a wonderful homage.”

A spokesperson for the state Public Safety Department said the monolith is clearly “somebody’s art installation, or an attempt at that.”

And yet, mystery also surrounds just how long the sculpture has been in the remote, rarely trafficked corner of Utah. The public safety spokesperson said it may have been there since the 1940s or the 1950s.

A user on Reddit, who goes by a name too profane to publish, claimed to have found the exact location of the sculpture through satellite images and terrain analysis. Based on the analysis, some believe it wasn’t placed in the canyon until after McCracken died.

And just as interest in the monolith seemed to be plateauing, another — perhaps a copycat — was discovered in Romania — the second monolith of what could be many more to come.

This content was originally published here.