The third strange monolith, possibly made of stainless steel, to appear out of nowhere was spotted Wednesday in California.
"There is currently a monolith at the top of Pine Mountain in Atascadero!" tweeted Connor Allen on Wednesday afternoon.
The Atascadero News reported that it was 10-feet tall and 18 inches wide, and could be pushed over.
Local media reported that the strange structure was removed Sunday night, but it's unclear who took it. Locals reported seeing “strange lights” in the area at the time, according to Jurnalfm.
The metal structure, which was between 9.8 feet and 13.1 feet tall, was near the ancient fortress Petrodava, the outlet said.
The first strange structure was originally spotted in Utah was also removed by an unknown party, the state's Bureau of Land Management confirmed.
During a site visit Saturday, a bureau team said an unknown person or group removed the illegally installed structure referred to as the "monolith" the evening of Nov. 27.
Estimated between 10 feet and 12 feet high and thought to be some kind of metal, it was discovered by state wildlife employees while they were counting sheep from a helicopter. The structure sparked comparisons with a similar-looking slab in Stanley Kubrick’s 1968 film “2001: A Space Odyssey."
Police won’t be opening a major investigation into the disappearance of the mysterious silver-colored monolith. Its creator also remains a mystery.
It drew crowds after the monolith was spotted Nov. 18 by state helicopter crews helping wildlife biologists count bighorn sheep.
Utah officials did not say specifically where the monolith was, but people soon found it through satellite images dating back to 2016 and determined its GPS coordinates.