The man who created the 'Storm Area 51' Facebook event says he was contacted by the FBI after jokingly calling on alien enthusiasts to raid the classified military base in Nevada.

Matty Roberts said he initially created the 'Storm Area 51, They Can't Stop All of Us' event in June as a joke but it quickly went viral.

More than two million people have since responded to the event and said they plan to attend next month.

Roberts said he was contacted by the FBI last week about his creation.

Matty Roberts said he initially created the 'Storm Area 51, They Can't Stop All of Us' Facebook event back in June as a joke but it quickly went viral

'The FBI showed up at 10am and contacted my mom, and she calls me like, "answer your phone the FBI is here",' Roberts told 23ABC.

'I was kind of scared at this point, but they were super cool and wanted to make sure that I wasn't an actual terrorist making pipe bombs in the living room.'

While it initially started as a joke, Roberts said it had morphed into an actual event for enthusiasts called the Alienstock Festival.

It will be held in the tiny Nevada town of Rachel on September 20.

'It's insane and I just created a joke while I was playing video games and it has taken off to this wild monster,' Roberts said.

'I want to make this something as a positive, enjoyable, safe and profitable for the rural area of Nevada.'

There is now an official website for the event and hotels in the surrounding area have already booked out.

More than two million people have since responded to the Facebook event and said they had plans to attend next month

Authorities have warned that those attending the event who do try to break into the Area 51 compound (above) will be arrested

'We're aiming to establish something unique here, a meeting place for all the believers,' the festival's website states.

'We want to host a Festival in Rachel, NV, the closest town to Area 51. They can't stop us from gathering and celebrating Aliens.'

Authorities have warned that those attending the event who do try to break into the Area 51 compound will be arrested.

Area 51 is the codename for the highly-classified remote detachment of California's Edwards Air Base, located 83 miles northwest of Las Vegas.

It was founded in 1955 as a test site for the Lockheed U-2 reconnaissance plane.

Since then, however, it has become the subject of numerous UFO sightings and has become inextricably linked in the public's mind with captive aliens and government conspiracies.

Famous machines developed there include the U-2 spy plane, SR-71 Blackbird, and the F-117A Nighthawk stealth fighter.

A convenience store named the Area 51 Alien Center is seen along U.S. highway 95 in Nevada near the highly-classified military base

Many conspiracy theorists claim the base has been used to research an alleged crashed alien spacecraft at Roswell, New Mexico, in 1947.

What takes place inside the heavy-duty fence at Area 51 has remained a mystery to anyone without high-level security clearance, save for a few photos taken illegally by curious conspiracy theorists.

In 2013 the US government admitted that the base is a secret intelligence hub when the CIA released an official history of the U-2 and OXCART projects, along with aerial photos of the site.

The facility experienced a rare security breach in January when an unidentified male sped through a checkpoint at the entrance.

Guards and Nye County police chased him at high-speed for about eight miles before he came to a stop and exited his vehicle.

He began advancing toward officers with an 'unknown cylindrical object' in hand and did not heed verbal warnings to stop, so security officials were forced to open fire.

He was pronounced dead at the scene.