After years of government denials, the CIA is officially acknowledging in newly declassified documents the existence of Area 51, the mysterious site in central Nevada that has spawned top-secret tools, weapons and not a few UFO conspiracies.

George Washington University's National Security Archive obtained a CIA history of the U-2 spy plane program through a public records request and released it Thursday.

National Security Archive senior fellow Jeffrey Richelson reviewed the history in 2002, but all mentions of Area 51 had been redacted.

READ: The newly declassified CIA documents

Richelson says he requested the history again in 2005 and received a version a few weeks ago with mentions of Area 51 restored.

Officials have already acknowledged in passing the existence of the facility in central Nevada where the government is believed to test intelligence tools and weapons.

Richelson believes the new document shows the CIA is becoming less secretive about Area 51's existence, if not about what goes at the location 90 miles north of Las Vegas.

He said that releasing information on the site "is clearly a conscious decision to acknowledge the name, the location rather than play pretend about the secrecy," the Las Vegas Review-Journal reports.

The references are found in a CIA history of the U-2 reconnaissance program written in 1992.

The history even recalls the first time CIA project director Richard Bissell and Air Force officer Col. Osmund Ritlandt spotted the site, which was then an old airstrip by the salt flat named Groom Lake.

They viewed it from aboard a small Beechcraft plane piloted by Tony LeVier, Lockheed's chief test pilot.

Excerpt

They spotted what appeared to be an airstrip by a salt flat known as Groom Lake, near the northeast corner of the Atomic Energy Commission's (AEC) Nevada Proving Ground.

After debating about landing on the old airstrip, LeVier set the plane down on the lakebed, and all four walked over to examine the strip. The facility had been used during World War II as an aerial gunnery range for Army Air Corps pilots. From the air the strip appeared to be paved, but on closer inspection it turned out to have originally been fashioned from compacted earth that had turned into ankle-deep dust after more than a decade of disuse.

If LeVier had attempted to land on the airstrip, the plane would probably have nosed over when the wheels sank into the loose soil, killing or injuring all of the key figures in the U-2 project.

The document says the group agreed that the location "would make an ideal site for testing the U-2 and training its pilots," according to the history.

The lightweight U-2 spy plane was being built by Lockheed at its top-secret "Skunk Works" plant in Burbank, Calif.

The document says that the CIA then called on the Atomic Energy Commission to add the Groom Lake area to its real estate holdings in Nevada.

"AEC chairman Adm. Lewis Strauss readily agreed and President Eisenhower also approved the addition of this strip of wasteland, known by its map designation as Area 51,to the Nevada Test site," according to the document.

"To make the facility in the middle of nowhere sound more attractive to his workers, (Skunk Works founder) Kelly Johnson called it the Paradise Ranch, which was soon shortened to the Ranch," according to the document.

Several books and articles in recent years had already begun to penetrate the mystery of Area 51.

In 2010, James Noce, who said he did contract security work at the site in the 1960s and 1970s, told The Seattle Times that he used to get paid in cash, signing a phony name to the receipt.

Noce, then 72, told the newspaper that he had attended the first-ever public reunion in 2009 of former Area 51 workers.

"I was doing something for the country," Noce says about those three years in the 1960s. "They told me, 'If anything should ever come up, anyone asks, 'Did you work for the CIA?' Say, 'Never heard of them.' But [my buddies] know."

Contributing: Associated Press