What started as a joke about storming the infamous Area 51 Air Force base has drawn the attention of U.S. military officials, who warned UFO seekers earlier this month to stay away from the compound in southern Nevada.

Now one of Nevada’s top elected officials is also urging people intending to “storm” the highly classified military base to think twice.

“Storming any kind of Department of Defense facility is not safe. It’s not safe for those who are guarding it, it’s not safe for what we’re protecting inside,” Sen. Jacky Rosen (D-Nev.) said on Tuesday.

Nearly 2 million Facebook users have now signed up to besiege the Nevada site, which has long been the center of conspiracies for those who believe it’s a holding site for extraterrestrial creatures.

“We can move faster than their bullets. Lets see them aliens,” the event description says. The purported raid is set for Sept. 20 between 3 a.m. and 6 a.m.

While the event is almost certainly a joke, it did prompt a warning from the Pentagon earlier this month. A spokeswoman for the Air Force said that anyone seriously intending to storm the site shouldn’t try their luck.

″[Area 51] is an open training range for the U.S. Air Force, and we would discourage anyone from trying to come into the area where we train American armed forces,” she said. “The U.S. Air Force always stands ready to protect America and its assets.”

Residents from the small town of Rachel, Nevada, which is just down the road from Area 51, have reported intense interest and increased business due to the Facebook event, which went viral. (The phenomenon has spawned another, similar call on Facebook to “find dat big boi” — the Loch Ness monster — in Scotland.)

Rosen did not, however, shed any light as to whether those who intend to storm Area 51 will be disappointed by what they find inside.

“I haven’t been to Area 51 myself. I appreciate that people shop along the highway for all those souvenirs,” she said, referring to the many alien-themed businesses set up along a road the state officially dubbed the “Extraterrestrial Highway.”

Nevada’s other senator, Catherine Cortez-Masto (D), similarly declined to weigh in on Area 51 and the purported mysteries surrounding it.

“I don’t know anything about what they’re looking for. I understand it was a joke,” she said when asked about the event on Wednesday.

A decade ago, the Pentagon set up a program to study encounters by the Navy with unidentified aircraft at the request of then-Sen. Harry Reid (D-Nev.). Three current U.S. senators received a classified briefing on those UFO sightings ― some of which were captured on video and made public ― last month.

“I personally don’t know if there exist little green men other places, I kind of doubt that, but I do believe that the information we have indicates we should do a lot more study,” Reid said in an interview in January. “We have hundreds and hundreds of people that have seen the same thing — something in the sky, it moves a certain way.”