The memo, dated March 22, 1950, was sent by FBI Washington, D.C., field office chief Guy Hottel to then-Director J. Edgar Hoover.
According to the FBI, the document was first made public in the late 1970s and more recently has been available in the "Vault," an electronic reading room launched by the agency in 2011, where it has become the most popular item, viewed nearly 1 million times. The Vault contains around 6,700 public documents.
Vaguely written, the memo describes a story told by an unnamed third party who claims an Air Force investigator reported that three flying saucers were recovered in New Mexico, though the memo doesn't say exactly where in the state. The FBI indexed the report for its files but did not investigate further; the name of an "informant" reporting some of the information is blacked out in the memo.
The memo offers several bizarre details.
Inside each saucer, "each one was occupied by three bodies of human shape but only 3 feet tall, dressed in metallic cloth of a very fine texture," according to the report. "Each body was bandaged in a manner similar to the blackout suits used by speed fliers and test pilots."
The saucers were found in New Mexico because the government had a high-powered radar set up in the area and it is believed the radar interfered with the controlling mechanism of the UFOs, according to the informant.
The FBI filed the typed page neatly away 63 years ago at its headquarters and "no further evaluation was attempted."
The memo does not appear to be related to the 1947 case in Roswell, N.M., when Air Force officials said they recovered a UFO, only later to recant and say it was a research balloon.
"For a few years after the Roswell incident, Director (J. Edgar) Hoover did order his agents at the request of the Air Force to verify any UFO sightings," the FBI said Thursday. "That practice ended in July 1950, four months after the Hottel memo. Suggesting that our Washington Field Office didn't think enough of that flying saucer story to look into it."
Online: 'The Vault' memo