US President Donald Trump did not confirm Bob Levinson's death, saying that Iran had not communicated any news on the former agent, who would have turned 72 this month, AFP reported.
"Iran has always maintained that its officials have no knowledge of Mr. Levinson's whereabouts, and that he is not in Iranian custody," said Alireza Miryousefi, chief press officer at Iran's mission to the United Nations.
"Those facts have not changed."
Levinson's family said that it had learnt that he was dead, although it gave no information on how or when.
"We recently received information from US officials that has led both them and us to conclude that our wonderful husband and father died while in Iranian custody," said a statement from the family.
The claim came as the White House in the past said that Levinson had left Iran following his 2007 visit to the country.
Levinson reportedly visited Iran’s southern Kish Island on March 9, 2007. He later went missing and his whereabouts have remained unknown ever since. There are different reports about the aim of his trip, with some saying the man, who had become a private detective, was reportedly investigating cigarette counterfeiting in the region. Others said he had been on a business trip, Press TV reported.
But The Washington Post reported in 2013 that Levinson, who had retired from the FBI, was working for the CIA and had gone on a rogue mission aimed at gathering intelligence on Iran.