The Central Intelligence Agency (CIA) whisked out Iranian scientist Shahram Amiri and another informant from Iran last in 2009 amid concerns that Tehran had discovered they were providing secrets to the US, according to a media report.
Amiri was among half a dozen sources who had provided information to the CIA from inside Iran's nuclear programme and were subsequently resettled in the US, the Washington Post reported citing unnamed current and former US officials.
All were given reward packages, including the $5 million set aside for Amiri. The funds were administered by financial firms outside the CIA's control, as part of CIA's efforts to gather intelligence on Iran, the influential US Daily said on Saturday.
Some of the agents were brought out of Iran because they wanted to relocate, but Amiri and a second informant were pushed to leave Iran after indications that they had come under suspicion by the country's Ministry of Intelligence and Security, the Post said.
"There was fear of exposure," a former senior US intelligence official familiar with the cases was cited as saying. One had gotten "sloppy" in his communications with the agency, the former official said, but even when told of the exposure risk remained in Iran "longer than we thought prudent".
The CIA is expected to conduct a damage assessment to determine whether any sources or methods were compromised by Amiri's return, the Post said.
If Amiri's information was being used in a widely anticipated assessment of Iran's nuclear weapons plans that has already missed several deadlines, the assessment could again be delayed, officials were quoted as saying.
When Amiri was resettled in the US, it was his decision not to try to bring his family, perhaps because those relations were strained, the Post said citing officials.
Once inside the US, defectors are typically allowed to choose where they want to resettle. The rewards they get are often based on promises made while they worked as spies, but are subsequently spelled out in memoranda drafted by the CIA's National Resettlement Operations Centre in the US, it said.