Update:Here is one of the slides
Unseen slides of 'Roswell alien corpse in crashed UFO' to be released today
YouTubeAlien autopsy images which were revealed as a hoax
Photographs, which claim to show the remains of an alien found dead by US authorities at a ranch near Roswell, New Mexico, in 1947, are being unveiled at a conference at the 10,000 seater National Auditorium in Mexico City, attended by Dr. Edgar Mitchell, the sixth astronaut to land on the moon.
The Roswell story, of the authorities keeping the discovery of the alien a secret from the public, has been long regarded an elaborate fake.
Pictures of an "alien autopsy" on the body released after the Roswell crash were later outed as an elaborate hoax.
Some UFO investigators claim today's release of new images will prove the truth of the myth.
They were allegedly photographed by geologist Bernard A. Ray on a Kodachrome film after he saw the body, but then stored the images in his attic for more than 50 years.
Anthony Bragalia, a UFO investigator, has been working to prove the authenticity of the incident for years.
He claims the "creature" pictured is not a being "that finds its origin on Earth".
Writing on his blog, he revealed: "Professionals from a range of disciplines who have seen the slides agree that they depict a small humanoid creature – a formerly living thing - that is not a prop nor a genetically defective human.
"This humanoid is not a deformed person, mummy, dummy, simian or dead serviceman."
He added: "What is depicted is really there, accurately reflected in the emulsion as an actual moment in time in 1947.
"Science has weighed in and has determined that these are real slides that are really from the year."
Chase Brandon, a CIA agent who served 35 years with the agency, believes the evidence that is about to be revealed will all be worth it.
YouTubeMore blurry images from the "autopsy" which proved to be fake
ROSWELLDAILYRECORDOriginal newspaper report from the time
It was in a vaulted area - there was one box that really caught my eye. It had one word on it: Roswell. It was a craft that did not come from this planet.
Chase Brandon, former CIA agent
Speaking in 2012, he described first seeing the slides, saying: "It was in a vaulted area - there was one box that really caught my eye. It had one word on it: Roswell.
"I rummaged inside it, put the box on the shelf and said, 'My God, it really happened.'
"It was a craft that did not come from this planet."
But others in the UFO investigation field fear the conference is another cynical, and money-spinning, hoax.
Nigel Watson, author of the UFO Investigations Manual, said: "There is already a considerable amount of cynicism and scepticism about these pictures, epecally since we have been promised the real evidence for the Roswell crash in the past, and they have turned out to be fakes and hoaxes.
"The so-called Alien Autopsy films of the recovered aliens from the crash, although very graphic, are now admitted to be re-enactments of the real film that got lost or destroyed. So that evidence is useless though still hotly debated in some quarters of ufology!
"As for these latest pictures, well the sceptics are out in force. One of the major niggles is that they are not being shown until the conference."
Nick Pope, a former UFO investigator at the UK's Ministry of Defence, told the Daily Mirror he has seen one of the images, but warned it could be another fake.
He said: "The blurry image I've seen shows a small figure, vaguely humanoid but with the disproportionately large head and eyes so often associated with the type of alien that the UFO lobby calls the trays."
YouTubeAnother view of faked Roswell autopsy
YouTubeLast year this video of a "UFO" of the back of a truck being driven near Area 51 appeared online.