( CNN ) The FBI has increased its reward for information on missing American Robert Levinson from $ 1 million to $ 5 million , it announced Monday . Levinson , a retired FBI agent , vanished after traveling to the Iranian island of Kish in March 2007 and is one of the longest-held U.S. citizens in history . The FBI announced the reward increase on the eighth anniversary of Levinson 's disappearance -- and the day before his 67th birthday . `` Levinson traveled to Kish Island , Iran , on March 8 , 2007 , working on behalf of several large corporations , and his whereabouts , well-being and the circumstances surrounding his disappearance have been unknown since that time , '' it said in a statement . U.S. Secretary of State John Kerry issued a statement asking Iran to cooperate with the investigation into Levinson 's whereabouts . `` He has spent more than 2,900 days separated from those who love him , and is one of the longest held U.S. citizens in history . Year after year , the family has endured the pain of his absence . It is time for him to come home , '' Kerry said . `` We remain committed to the safe return of Mr. Levinson to his family and appreciate the support and assistance from our international partners . We remain concerned about Mr. Levinson 's health given his age and the length of his disappearance . '' Iran 's government repeatedly has said it is not holding Levinson and does not know his whereabouts . The FBI says he was in Iran as a private investigator . But news reports in 2013 said he was working as an independent CIA contractor when he disappeared . That prompted his family to speak out , saying they kept it quiet for years that Levinson was working for the CIA , because the U.S. government had warned them that revealing it would put him in more jeopardy . The FBI , White House and CIA have not publicly acknowledged any connection between the CIA and Levinson . It 's unclear exactly who is holding him , but U.S. officials have said they believe he is somewhere in southwest Asia . Whoever his captors are , in 2010 they sent a `` proof of life '' videotape and photographs of Levinson to his family . In the video , he asked the U.S. government for help : `` Please help me get home , '' a gaunt-looking Levinson said on the tape , citing his 33 years of service in the FBI as a reason for that help . The photographs showed him with a large beard .
The FBI says it is increasing the reward for missing American John Kerry to $ 5 million . Levinson , a former FBI agent , went missing in Iran eight years ago ; Iran says it does not know where he is . Secretary of State Robert Levinson has issued a statement asking for Iran to cooperate in the search for Levinson .