Ex-FBI agent’s family is still hoping for answers after he disappeared in Iran in 2007

Robert Levinson’s family said they were disappointed he was not one of the freed prisoners

Ex-FBI agent Robert Levinson disappeared almost 9 years ago (AP)

The family of an ex-FBI agent who disappeared in Iran almost nine years ago spoke of their dashed hopes that he was not one of the prisoners freed by Tehran over the weekend.

Robert Levinson went missing on 9 March 2007 and was last seen on the Iranian resort of Kish Island. He was reportedly on an unauthorized mission for the CIA.

Mr Levinson’s wife, Christine, said she does not believe Iranian officials who say they do not know where her husband is.

Tehran secured the release of four prisoners from Iran in exchange for the US pardoning or dropping charges against seven Iranians. A fifth American, a student who was held for 40 days, was also released separately.

Mrs Levinson said she wished the US government had warned the family that her husband would not be among the freed prisoners.

“It was especially heartbreaking as we had to learn it on our own, from TV,” she told CNN.

The former agent's son Dan told the same news channel that the search for his father has spanned two Presidential administrations. He said he worried that now the nuclear deal with Tehran was over, the attention on his father would be lost.

“He doesn’t deserve this. He was serving his country and he needs to be prioritized,” he said.

Mr Levinson’s family last saw photos of him alive five years ago, and say he has health problems including diabetes, gout and high blood pressure.

The family retraced his steps in 2009 on the small Kish Island and the five-minute drive to the airport and Mr Levinson’s hotel, and they believe there must be some knowledge of his location.

Secretary of State John Kerry has said the US would continue to search for him.

The freed prisoners comes as the US has lifted sanctions on Iran after it was confirmed that Tehran had stuck to an agreement over a nuclear deal.