Robert Levinson, missing Ex-FBI agent, is alive

(CBS/AP) WASHINGTON - After nearly four years without word about what happened to retired FBI agent Robert Levinson, his family received proof late last year that the father of seven was alive.

Until then, there had never been any evidence about whether Levinson was alive or dead since he disappeared in March 2007 from the Iranian island of Kish. It remains unclear who is holding Levinson or where he is, but the proof that he is alive was a hopeful sign that whoever has him was willing to negotiate for his release.

"Our family is tremendously encouraged by the news Bob is alive but remains concerned for his safety and well being," his wife, Christine, said in a statement on the family's website.

The Associated Press has known about the proof that Levinson is alive since shortly after it arrived but delayed reporting it because officials said any publicity would jeopardize getting Levinson home safely. The AP is not disclosing the nature of the proof because officials believe that would hurt efforts to free him.

On Thursday, the State Department issued a three-sentence statement by Secretary of State Hillary Clinton saying there were indications Levinson was in southwest Asia and asking Iran for help.

Iran has repeatedly said it has no information about Levinson, but U.S. diplomats and investigators have long said they believed he was taken by Iranian government agents. The U.S. announcement Thursday was an abrupt change in tone from what had been stalemated discussions. The U.S. has previously expressed deep frustration over what it said was Iran's lack of cooperation.

Levinson disappeared after a meeting with Dawud Salahuddin, an American fugitive wanted for the assassination of a former Iranian diplomat in Maryland in 1980. Salahuddin has said he last saw Levinson being questioned by Iranian officials. Levinson's distinctive signature was used to check out of his hotel, but he never made it to the airport.

As years passed, many in the U.S. government believed the 62-year-old with diabetes and high blood pressure might have died. With proof that he is alive, the case becomes one of the longer international hostage situations involving U.S. citizens. Levinson is unusual, however, since nobody has publicly acknowledged holding him.

"It's encouraging that we may have good news," Florida Sen. Bill Nelson said. "I'm praying that he can be reunited with his family."