The CIA has released thousands of declassified documents on flying saucers, aliens and other unexplained phenomena.
'We've decided to highlight a few documents both skeptics and believers will find interesting,' the agency said on its website.
The post continued: 'Below you will find five documents we think X-Files character Agent Fox Mulder would love to use to try and persuade others of the existence of extraterrestrial activity.'
All of the documents are dated from the late 1940s to the 1960s, but were top-secret until now.
One of the files attached to the post is a document from East Germany in 1952, where agents were called to investigate what witnesses described as a 'huge flying pan'.
The object was said to have a diameter of about 15 meters, according to the document.
Similar flying saucers were also spotted in North Africa and Spain, the report said.
'The picture [of the object] shows a diagonal stripe of diminishing width and lighter in shade than the sky over the dark bulk of a building cornice,' it was noted.
Included with some of the documents were three pictures of the alleged extraterrestrials.
One of the photos - taken by British student Alex Birch in 1962 - claimed to show a group of flying saucers flying over the city of Sheffield in the UK.
However the photo was proven to be a hoax.
The files also detail a case of flying saucers that were spotted over what was formerly Belgian Congo.
The document reveals that two 'fiery discs' were seen over a uranium mine, and that the discs had 'glided curves and changed position many times'.
It then adds: 'Suddenly, both discs hovered in one spot and then took off in a unique zigzag flight to the north east.
'A penetrating hissing and buzzing sound was audible to onlooker below. The whole performance lasted 10 to 12 minutes.'
An aircraft was then set to investigate the object, and got with meters of the saucer and according to the pilot, the inner core of it remained totally still while the a knob opening could be seen from the outside.
The pilot then gave up his pursuit when the 'disc' appeared to disappear.
Also contained in the files is the case in Socorro, New Mexico in 1964, when police officer Lonnie Zamoraspotted a large flame rise from the ground and pierce the sky above a remote patch of desert.
He went to investigate and found a shiny object the size of a sedan perched on the hilltop, which was oval in shape and aluminium in color.
The object then began to rise into the air and then sped away from him over the mountains and disappeared.
The release of the documents coincide with the long-awaited return of The X-Files on Sunday.
The beloved show was rebooted by the Fox Network after 10 years, with its two original stars reprising their roles.