Former FBI agent Robert Levinson, who disappeared in Iran 13 years ago, has died in custody there, according to statement from his family, BBC reported.
"It is impossible to describe our pain," the family said, adding that his death appeared to have occurred before the coronavirus pandemic.
Levinson, the longest-held hostage in US history, disappeared in 2007 on the Iranian island of Kish.
His family say he was working on behalf of an unauthorised CIA mission.
He retired from the FBI in 1998, but had been working in Kish as a private investigator, looking at cigarette counterfeiting in the region, his wife says.
US officials suspected he was kidnapped by Iranian intelligence forces to be used as a bargaining chip in dealings with Washington.