The UFO explosion of 1949: FBI secret files
London: Secret FBI files that have been made public for the first time reveal that US police and army officers saw a UFO explode over Utah state in 1949.
On April 4, 1949, FBI special agents sent a cable marked "urgent" to the bureau director, Edgar Hoover.
The document spoke of how an armyman, a policeman and a highway patrol, who were all miles apart, each saw a UFO, which they said exploded over mountains near Logan, north of Salt Lake City.
The memo is part of thousands of previously unreleased files that the FBI has made public in a new online resource called "The Vault". according to the Daily Mail.
The document said the three men each "saw a silver coloured object high up approaching the mountains at Sardine Canyon" that suddenly exploded.
An earlier UFO sighting had been investigated in Logan in September 1947.
Many witnesses told the FBI they saw "flying discs" in formation that were "circling the city at a high rate of speed".
A memo from a special agent in charge of the Washington field office sent in 1950 says aliens landed at Roswell in New Mexico.
The aliens came in flying saucers, the memo said.
"They were described as being circular in shape with raised centres, approximately 50 feet in diameter. Each one was occupied by three bodies of human shape but only three feet tall."
The bodies were "dressed in a metallic cloth of a very fine texture. Each body was bandaged in a manner similar to the blackout suits used by speed flyers and test pilots".
Roswell in New Mexico became famous after reports that a flying saucer had crashed in the desert near a military base in July 1947.
The bodies of aliens were said to have been recovered and autopsied by the US military, but American authorities allegedly covered the incident up.
Another report said a flying disc "hexagonal in shape" and "suspended from a balloon by a cable" was seen in the area.