It's the conspiracy theory that just won't go away: that the U.S. government is, deep in some secret location, keeping the bodies of alien astronauts recovered from the crash of a flying saucer in New Mexico in 1947.

The "Roswell Incident," named for the small town near where some wreckage was found - a weather balloon, the U.S. military says; a UFO, say those who, well, believe it was a UFO - was back in the news this week when two photographs, claimed to be of preserved alien remains, were presented at a UFO conference in Mexico City.

The photos, taken on Kodachrome color slide film, have been confirmed as being on film stock from the late 1940s - but that doesn't mean the alien claim is true, experts say.

What is much more likely, they say, is that the photo is in fact a 1940s image - but of a human child's mummified body.

As evidence that the alien claim is either a publicity stunt - a documentary film Roswell Slides is in production - or a hoax, scientists noted that attendees at the Mexico City conference who wanted to view the color slides had to cough up $350 for the privilege.

The skeleton in the photos does have a large head in relation to the rest of the body, but that's a characteristic of any child's body, experts say.

Mummified children's bodies have been mistaken for aliens before, but even those with strange, deformed skulls have a simple explanation; cranial deformation was widely practiced by many ancient human civilizations.

Still, many UFO adherents are standing by the claims made in Mexico City.

"(These photos) show the human race, beyond any doubt, that extra-terrestrial visits are a reality," said Jaime Maussan, a Mexican UFO researcher who hosted the conference.

"That is why the presentation of two slides, two transparencies, where a being with nonhuman features can be seen, is very important."

Despite years of research by the U.S. Air Force and other agencies that have found to evidence of aliens - or UFOs - many still hold to their conviction that the government is covering up the existence of a flying saucer or its occupants - or both - in a secret hangar at Area 51 in Nevada.

The newly released photos are unlikely to change anyone's mind one way or the other, of course. That's just the nature of conspiracies. They're hard to prove; the problem is they're also hard to disprove.

The photos were said to have been taken by geologist Bernard Ray between 1947 and 1949, and the images were found inside a box that also contained images of Bing Crosby, Clarke Gable and Dwight Eisenhower from before his term as president. The box was located in the attic of a house in Sedona, Ariz. A team of UFO specialists says they are authentic.

Artwork by Frank Kovalchek | Flickr