Despite repeated warnings from law enforcement officials and the U.S. Air Force, people have begun descending upon two small desert towns in the western U.S. state of Nevada.
Local media reports said people in campers and trucks have begun to set up camp near Rachel and Hiko, Nevada, with a combined population of little more than 150.
They are there to heed the call of "Storm Area 51, They Can't Stop All Of Us," an internet joke that has gone viral.
The Facebook event set up by college student Matty Roberts invited people to attempt to run into the mysterious site at 3 a.m. Sept. 20.
"If we Naruto run, we can move faster than their bullets," the event description says, referring to a Japanese comic character known for running with his arms stretched out backward and his head forward.
Roberts told the Los Angeles Times, ""I sparked a movement while I was bored at 2 a.m." But his idea took on a life of its own.
More than 2.1 million have said on the Facebook page that they plan to attend.
Roberts has since disassociated himself from the event, citing public safety concerns because the towns lack infrastructure to support a visit by tens of thousand, or maybe more.
Area 51 is part of the vast Nevada Test and Training Range that provides "flexible, realistic and multidimensional battlespace'' for testing and "advanced training in support of U.S. national interests,'' according to the U.S. Air Force.
It has been the subject of conspiracy theories that say the U.S. military keeps aliens and UFOs there.
After decades of government officials refusing to acknowledge Area 51, the CIA released declassified documents in 2013 referring to the 20,700-square-kilometer installation by name and locating it on a map near the dry Groom Lake bed.