The bombshell claims have sent conspiracy theorists, who believe the document could be genuine, into overdrive.
Today, Express.co.uk revealed how the alleged 47-page document emerged today, including a report that claimed the 1947 Roswell UFO crash actually happened and was covered up.
A six-page section on Roswell said the US military recovered fragments of a destroyed flying saucer outside Roswell and four decomposed aliens.
The full report claims a further six UFOs have been found and 23 more bodies.
The document, which has already been branded an elaborate hoax by some UFO experts, also includes a four-page report on an alleged top-secret group set up by the DIA in the wake of the Roswell incident.
Operation Majestic 12 is said to be an “above top-secret” intelligence group set up to investigate “alien visitations of earth” by order of President Harry S Truman in September 1947.
The four page report, said to have been prepared on January 8, 1989, claims to be a preliminary briefing about Majestic 12.
It states: “Advanced beings of non-human nature are continuously being detected along with their flying disc craft in the controlled air space of the US since July 7 1947.
“The remain of seven flying craft and the bodies of 27 non-human beings have been recovered as of this briefing date, and are at present being studied by Majestic-12 scientists.
“Three of the recovered craft are nearly intact and one such machine has maintained some of its power since retrieval in 1948.
“Since 1957, no additional alien craft have been available for study.
“The assessment is that these beings have adapted or perfected these machines to the conditions of our world as to avoid any further such revealing crashes.”
The document said six senior military officials and six private sector scientists, all unnamed, made up the group, which was operating at sites across the country, including the NASA Ames Research Centre in California.
The document is said to have been given to Heather Wade, host of US late-night online paranormal radio show Midnight in the Desert., from a known source who has not been named.
Seasoned UFO expert and nuclear physicist Stanton Friedman is investigating the authenticity.
The Paridigm Research Group (PRG) which tries to pressure the White House to disclose documents about UFOs believes the report could be genuine, but accepts it could also be fake.
Express.co.uk has contacted the DIA and awaits a response.