Perhaps aliens got lost on the way to Area 51.

An elaborate crop circle in a barley field about six miles southeast of Salinas appeared to have landed from out of nowhere Monday, when a YouTube video depicting its alleged discovery made its way onto the Internet.

By late afternoon, news of the circle outside Chualar had drawn curious onlookers from throughout the Salinas Valley.

Stamped in the middle of the field, the design covered about an acre and looked like a strange computer chip with dots in the middle that some Internet observers interpreted as either Braille or Morse code.

Most crop circle enthusiasts were quick to call it a hoax. But with the landowner apparently unaware of how it happened, theories were multiplying all over the Internet by press time.

Security guards from San Jose-based Echelon Security were outside the property Monday morning. They said they could not reveal their client, only that they had been hired to stop the area from "becoming a circus."

Ben Johnson, one of the guards, said the circle appeared either Sunday or Monday morning.

The guards were happy to lead reporters to the circle. From ground level it looked like nothing but trampled-on grass cut at different angles.

A representative from the company at its San Jose headquarters said he could not reveal when the firm was hired or who the client was.

The property belongs to Scott and Debbie Anthony. Reached at home where she was ill in bed, Debbie Anthony said she'd heard about the spectacle but knew nothing other than what she was seeing in news reports. Scott Anthony could not be reached for comment.

A man who identified himself as Hector at the ranch office said he had not been able to get out to the field to inspect the design.

In the 2½-minute YouTube video posted Monday morning, two men appear to drive along Chualar Canyon Road before sunrise and see flashing lights in a field.

They get out of a compact car, hop a fence and enter a pushed-down area of weeds on a cultivated field.

"Dude," says one man, "are you seeing this?"

Among the first people to spot the crop circle from above were Julie and Pat Belanger, co-owners of the 111th Aerial Photography Squadron company.

Julie Belanger said they were flying in a Robinson R44 helicopter from South County Airport in San Martin toward Carmel when they spotted the circle.

"Flying through that area is not always very exciting," Belanger said, "and then, all of a sudden, that thing's there."

She said she had never seen anything like it in 20 years of aerial photography.

"I don't know about aliens," she said, "but someone very creative put it there."

Joe Pezzini, chief operating officer of Ocean Mist Farms, one of the largest growers in Monterey County, said he'd "never heard about (crop circles) around here."

The circles are typically discounted as hoaxes, and at times their creators come forward. But there are dedicated researchers throughout the country who try to verify their authenticity.

Jeffrey Wilson of the Independent Crop Circle Researchers Association said there was a "dead giveaway" this circle was a hoax.

He said it was too aligned with the man-made road, looked like human-invented Braille in the center, and the YouTube clip seemed similar to guerrilla-marketing techniques Wilson has seen.

"My guess is that ... it is commissioned work for an advertisement," he said. "Or a commissioned work for a production company making a documentary on crop circles or for some kind of film."

Wilson said it seemed to fit the mold of one professional crop circle-making group, Circlemakers.org, which has done work for the BBC, Nike, History Channel and others.

An email sent late Monday to the company was not answered by press time.

Crop circle researcher Nancy Talbott of the BLT Research Team in Cambridge, Mass., said that at first glance the Chualar circle appeared man-made.

"I looks very mechanical," she said. "... It doesn't look the way most of the genuine circles I've worked on look. That doesn't mean I'm right."

She said it could only be verified as authentic if she and her team could inspect the field and run tests.

Talbott said her group, which has studied thousands of crop circles since the 1990s, looks for physical changes in plants and soils. She said her group believes the changes are caused by very brief bursts of extremely intense heat.

Crop circles have been a phenomenon among UFO and paranormal activity enthusiasts since the mid-1970s, according to a lengthy 2009 article on the subject in Smithsonian magazine.

Theories about their origins include suggestions the circles are landing platforms for UFOs or Mayan symbols signaling the end of the world.

Yet there have been scattered reports of strange symbols in agriculture fields since the 17th century, the Smithsonian article said.

The Monterey County Sheriff's Office, the California Highway Patrol and Salinas Municipal Airport said they had not received reports about the circle and no neighbors reported hearing any abnormal sounds.

Security guards with Echelon said they did not receive reports of vandalism. Their main task was to guard the scene until an expert could arrive to determine how exactly the circle was made.

Staff writer Virginia Hennessey contributed to this report.