Last updated at 6:47 p.m. EST
Theand wounded six more at a remote outpost in southeastern Afghanistan had been invited onto the base and had not been searched, two former U.S. officials have told The Associated Press.
A former senior intelligence official says the man was being courted as an informant and that it was the first time he had been brought inside the camp.
The official says a senior and experienced CIA debriefer came from Kabul for the meeting, suggesting that the purpose of the session was to gain intelligence.
The former intelligence officials and another former official with knowledge of the attack spoke on condition of anonymity because they were not authorized to speak publicly.
The Central Intelligence Agency would not confirm the details, and said it was still gathering evidence.
"It's far too early to draw conclusions about something that happened just yesterday," said spokesman George Little.
A separate U.S. official suggested the bomber may have set off the explosives as he was about to be searched.
The bombing was expected to deal a major psychological, if not its ability to collect valuable intelligence on Taliban and al Qaeda forces operating along Afghanistan's eastern border with Pakistan. Officials credit the base with providing some of the intelligence which has enabled CIA drone strikes to eliminate much of al Qaeda's top leadership, reports CBS News correspondent David Marin.
The CBSNews.com Special Report: Afghanistan Martin reports Afghan soldiers and civilians are present at almost every American outpost since one of the chief principals of the U.S. strategy is to partner with the Afghans. According to Christine Fair of Georgetown University, some of them may actually be
In a letter to CIA employees released by the agency, Mr. Obama said the U.S. would not be able to maintain its freedom and security without their service. He also noted that the spy agency has been tested "as never before" since the Sept. 11 attacks.