"Information obtained through exhaustive records searches and interviews indicated the material recovered near Roswell was consistent with a balloon device of the type used in a then-classified project," said a Pentagon statement. "No records indicated, or even hinted at, the recovery of 'alien' bodies or extraterrestrial materials."
In another statement Wednesday, Donna Hare, a former NASA contract employee, said that Apollo astronauts saw an alien craft when they landed on the moon, but were told not to reveal it. Hare's source was a man who had been quarantined with the astronauts.
Former Air Force Maj. George Filer III told reporters that when he was at McGuire Air Force Base in New Jersey, an alien craft came down, and an alien got out and was shot by a military policeman.
"Our security police went out there and found him at the end of the runway dead," Filer said.
"They asked me to brief the general staff," he said, but was later told not to. He said he would tell the story in front of Congress.
Filer is not new to UFO sightings. He has his own Web site called Filer's Files, where he says he also chased an alien ship over England when flying for the U.S. Air Force.
"I personally have observed a UFO both visually and on radar. I've been chasing them ever since," he writes.
Greer said extraterrestrials could provide a new, plentiful source of energy that would supply the world's energy needs.
Information from alien encounters, said Greer, could also have significant impact on the global environment and the quest for world peace.
ABCNEWS' Katelynn Raymer in Washington and David Ruppe in New York contributed to this report.