Four years after a retired FBI agent vanished in Iran, US officials have received proof he is alive, intensifying secret negotiations to bring him home.
The US had lacked reliable information about whether Robert Levinson was alive. He disappeared in March 2007 from the Iranian island of Kish. It remains unclear who is holding Mr Levinson or where he is, but the proof that he is alive is a rare, hopeful sign in a case that had seemingly gone cold.
The State Department said on Thursday that it had indications Mr Levinson was in south-west Asia. It asked Iran for help.
Iran has repeatedly said it has no information about Mr Levinson, but US diplomats and investigators say they believe he was taken by Iranian agents.
Many in the US government believed the 63-year-old with diabetes and high blood pressure might have died. But late last year, Mr Levinson's family received proof he was alive.
Authorities do not know why the evidence that Mr Levinson was alive had surfaced after years of silence.
The case has become one of the longer international hostage situations involving US citizens. No one has publicly acknowledged holding Mr Levinson.
The US has expressed deep frustration over what it has said is Iran's lack of co-operation.
The Iranian President, Mahmoud Ahmadinejad, has been circumspect about what his country knows about Mr Levinson. In one interview, he said he had no information, offered to help and then accused the FBI of withholding information about why Mr Levinson was in Iran.
Mr Levinson retired from the FBI in 1998 and became a private investigator. He was investigating cigarette smuggling in early 2007 and his family has said that effort took him to Iran.
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