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The NBC report, which cited unidentified sources claiming to have been “familiar with the management” of the human asset, maintained that he was a Sudan-born driver and confidante of Omar Abdel-Rahman, the “Blind Sheik” tied to the 1993 bombing of the World Trade Center in New York.

One retired senior FBI official said the overall revelation has caused a stir among officials who once worked in the U.S. counterterrorism community, and suggested the bin Laden source’s relevance may have simply been overlooked in the early 1990s.

“It’s interesting from this perspective when you look back at any major case. There’s always things there that in hindsight become very clear, but at the time when you’re in the middle of it, it’s meaningless,” the retired official said.

Edward J. Curran, a former top official in the FBI’s Los Angeles office, revealed the existence of the asset during a discrimination lawsuit filed against the bureau by Mr. Curran’s former agent, Bassem Youssef.

Mr. Youssef remains with the FBI, overseeing its telephone intercept analysis unit, and he won an appeals court ruling a few years ago to pursue the discrimination lawsuit against the bureau.

The bin Laden revelation is not the only startling discovery during Mr. Youssef’s case. In a separate revelation, Mr. Youssef wrote to the court that the FBI had been granted a Foreign Intelligence Surveillance Act warrant to spy on Abdel-Rahman nine days before the 1993 World Trade Center bombing.

The sheik’s followers were convicted on charges related to the bombing.

Like the FBI bin Laden source, the notion that the agency was watching the sheik when the 1993 bombing was executed was never mentioned in the more than 500-page official report by the 9/11 Commission.

The retired senior FBI official who spoke with The Times, meanwhile, said it would be worthwhile for the new panel to examine exactly what the bureau has in its historical files with regard to internal reporting generated during Mr. Youssef’s work at the bureau during the early 1990s.

“That’s what I would be looking at if I were on the [panel],” the former official said. “That’s what I would ask for, for sure, to see if they would give it up. I don’t know if they would.”

Mr. Meese said Wednesday that the panel will examine the issue because one of the mandates under the 2013 appropriations bill is to dig into “what evidence wasn’t known to the 9/11 Commission.”

During a hearing before the House Appropriations subcommittee that funds the FBI on Wednesday, Mr. Meese said the panel’s work will be framed by that and three other mandates: judging the FBI’s success in implementing 41 recommendations put forward by the 9/11 Commission, analyzing the bureau’s response to domestic terrorism since 9/11 and examining the FBI’s overall intelligence-sharing and counterterrorism policies.

Mr. Hoffman told lawmakers that while the past decade has seen the FBI adopt a “much more intelligence-driven approach” than it had prior to 9/11, as “the types of threat that we face are constantly changing and evolving.”

He added, however, that the FBI’s overall counterterrorism success speaks for itself.

“I think the proof is in the pudding. I don’t think in the dark days following the Sept. 11, 2001, attacks that anyone imagined that we would go this long without a major terrorist attack.”