Fears that thousands of alien hunters could attempt to “storm” Area 51 after responding to a viral Facebook event have proved unfounded, with fewer than 200 people turning up at the gates of the secretive US military base.
Most of those left peacefully after "heated warnings" from police, although authorities said two people were arrested at perimeter of the remote facility in Nevada.
It was a far cry from the millions who signed up to Storm Area 51, a joke Facebook event which suggested attendees “all meet up” to “see them aliens” at the base which conspiracy theorists claim holds evidence of extraterrestrials.
The event page was later shut down following condemnation from American authorities and locals, who feared a “disaster” if huge crowds descended on the harsh desert area where internet, phone signal and credit card facilities are scarce.
But the invitation nonetheless spawned alien-themed festivals in the tiny Nevada towns of Rachel and Hiko nearest the military site.
Lincoln County Sheriff Kerry Lee estimated that about 1,500 people had gathered at the festival sites and said more than 150 people also made the rugged trip several additional miles on bone-rattling dirt roads to get within selfie distance of the gates.
Another group of about 40 people gathered at a different gate in the Amargosa Valley.
The military had issued stern warnings that lethal force could be used if people entered the Nevada Test and Training Range, and local and state officials said arrests would be made if people tried.
"It's public land," the sheriff said. "They're allowed to go to the gate, as long as they don't cross the boundary."
A music group called Wily Savage erected a stage on Thursday near the Little A'Le'Inn in Rachel and began playing after dark for several hundred campers who braved overnight temperatures about 7C.
Guitarist Alon Burton said: "It started as a joke, but it's not a joke for us. We know people will come out. We just don't know how many."
Daniel Martinez, 31, a Pokemon collectible cards dealer from Pomona, California, was among those dancing in the makeshift festival grounds.
"Here's a big open space for people to be," he said. "One person starts something and it infects everybody with positivity. Anything can happen if you give people a place to be."
The entertainment kicked off weekend events that also feature a gathering Friday and Saturday at the Alien Research Centre souvenir store in Hiko.
Owner George Harris said it would focus on music, movies and talks about extraterrestrial lore.
Authorities reported no serious incidents related to the festivals, which were scheduled to last until Sunday.
Hiko and Rachel are about a 45-minute drive apart on a state road dubbed the Extraterrestrial Highway, and a two-hour drive from Las Vegas.
Michael Ian Borer, a University of Nevada, Las Vegas, sociologist who researches pop culture and paranormal activity, called the festivities sparked by the internet joke "a perfect blend of interest in aliens and the supernatural, government conspiracies, and the desire to know what we don't know."
"People desire to be part of something, to be ahead of the curve," he said. "Area 51 is a place where normal, ordinary citizens can't go. When you tell people they can't do something, they just want to do it more."
Eric Holt, the Lincoln County emergency manager, said he believed authorities could handle 30,000 visitors at the two events. Still, neighbours braced for trouble after more than two million people responded to the "Storm Area 51" Facebook post weeks ago.
"Those that know what to expect camping in the desert are going to have a good time," said Joerg Arnu, a Rachel resident who can see the festival grounds from his home.
Those who show up in shorts and flip-flops will find no protection against "critters, snakes and scorpions," he warned.
"It will get cold at night. They're not going to find what they're looking for, and they are going to get angry," he added.
The Federal Aviation Administration closed nearby airspace, although Air Force jets could be heard in the sun-drenched skies, along with an occasional sonic boom.