It was first spotted in a Utah desert. Then, Romania.

Now, it's in California.

Is it part of a product endorsement - or something out of this world?

A third mysterious metal pillar has been found on top of a mountain in California.

According to the Atascadero News, the three-sided structure in California was "welded together at each corner, with rivets attaching the side panels to a likely steel frame inside," The Guardian quoted the local daily as saying. The monolith is 10 feet tall, 18 inches wide and is made of stainless steel.

No one has been able to shed light on how the steel structure made it to Pine Mountain in Atascadero, let alone how it was carried to the top of a 1,300-foot hill. The monolith could be a hazard to people, local officials said.

Reports say the new obelisk on Pine Mountainin, located between the Bay Area and Los Angeles, is almost identical to the one found in Utah - but the haste at which it was seemingly set up resembles that of its Romanian twin.

Mike Orvis, president of the Atascadero Land Preservation Society, said his group doesn't have any information on the structure, including when it was found or the person or persons who placed it there.

The Astacadero News said the California pillar "could be knocked over with a firm push." Local reports estimate the monolith weighs around 200 pounds.

Internet sleuths have found it quite a challenge to make headway establishing the structures' origins, since the Utah and Romania pillars both disappeared days after their discovery.

A Colorado photographer said he saw four men dismantle the monolith in Utah and loaded the parts on a wheelbarrow. No one knows who removed the monolith in Romania.

This year continues to be "an interesting year - a mystery indeed," Orvis wrote in an email to The Tribune.

In the meantime, no one - not an ad agency, artists, pranksters, movie company, the scientists at NASA or extraterrestrial beings - has claimed responsibility for these unexplained objects.