If confirmed, the Iranwire report would fill in some gaps in what is known about the prisoner release, in which five people, including four Iranian-American dual citizens, were released by Iran, and seven people, including six Iranian-American dual citizens, were released by the United States.

Iranwire was created by Iranian journalists living outside the country, which exerts strict controls on the domestic news media. The founders include Maziar Bahari, an Iranian-Canadian who was himself a prisoner in Iran. It has maintained numerous contacts inside Iran.

Mr. Bahari said in a Twitter post that Iranwire had waited to report on Mr. Khosravi’s background until it knew he was safely out of Iran.

It described Mr. Khosravi as a former soldier in his 50s who was deployed in northeast Iran after the country’s revolution in 1979, and who like many others left Iran in the 1980s for the United States. It said he moved to California, home to a large Iranian expatriate community, became known as Fred Khosravi, and worked in the carpet business as a designer and seller in California and Florida. The account quoted his Tehran cellmate as saying Mr. Khosravi had told him that he later went to work as a freelance consultant to the F.B.I., returned to Iran in late 2013 to visit his aged mother in Tonekabon, a city near the Caspian Sea, and decided to stay there and teach English.

When Mr. Khosravi saw a BBC report about Mr. Levinson, a former C.I.A. and F.B.I. operative who has been missing in Iran since March 2007, the account said, he got in touch with an old F.B.I. contact to say he knew Mr. Levinson’s whereabouts. When interrogated by Iranian officials about this later, the account said, he claimed to have been under the influence of alcohol and had lied to impress his F.B.I. contact.