The FBI has found no evidence that anyone in the United States other than the 19 hijackers knew of the Sept. 11 plot ahead of time, Director Robert S. Mueller III told the congressional inquiry into the attacks.
The public release of his comments Thursday came as top CIA and FBI counterterrorism officials defended their agencies to lawmakers.
After Sept. 11, authorities rounded up hundreds of people nationwide on suspicion of links to Al Qaeda, terrorism or the attacks.
"To this day we have found no one in the United States except the actual hijackers who knew of the plot and we have found nothing they did while in the United States that triggered a specific response about them," Mueller said in testimony given in secret in June.
While that might seem to indicate that Zacarias Moussaoui was unaware of the attacks, Mueller prefaced his statement with the caveat that none of his comments were meant to include Moussaoui. The French-Morrocan man was arrested in Minnesota a few weeks before Sept. 11 and is now charged with conspiracy in the attacks.
FBI spokesman Bill Carter refused to clarify the director's remarks, saying they "speak for themselves."
On Capitol Hill, members of the House and Senate intelligence committees questioned Cofer Black and Dale Watson, who oversaw counterterrorism efforts of the CIA and FBI, respectively, before and during the Sept. 11 attacks.
Black, who helped capture Carlos the Jackal and survived an Al Qaeda plot to kill him in Sudan in 1995, said CIA officers were overwhelmed but did an excellent job with the limited resources they had.
Despite limitations, intelligence officials had successes, including thwarting a 1998 attack on the U.S. embassy in Albania, a millennium plot in Jordan and uncovering threats to the U.S. embassies in Yemen and France last year, he said.
Noting that he had been offered -- but declined -- an opportunity to testify anonymously behind a screen, Black said, "I want to look the American people in the eye."
The appearances of Black and Watson came after Eleanor Hill, staff director of the committee's inquiry, issued three reports over the past week outlining missed clues and warnings that could have led the CIA, FBI and other agencies toward the Sept. 11 hijackings.
Tensions peaked when disparate agendas of senators and representatives became apparent.
Sen. Pat Roberts, R-Kan., told Black that a hearing briefing book prepared by inquiry staff predicted Black would "dissemble" if asked certain questions. Roberts read a dictionary definition of dissemble that included "to hide under a false appearance."
Roberts, who has repeatedly expressed concern that the hearings would only demoralize intelligence agencies during wartime, then offered his personal apology for what he described as "the unintended consequences of what I believe is an inspector general runaway train."
Hill, who is directing the inquiry, is a former Pentagon inspector general.
"I won't call it shameful, but it's damn close," Roberts said.
Black responded that "something's getting out of hand here."
"Things happen," Black said. "People die in war. No one regrets that more than us. But dissemble? Mislead our people? No, it's like living a nightmare. What's going on here?"
Watson, retiring from his post as chief of the counterterrorism division, said no defense against terrorism will be ever be perfect.
"We don't do everything always right," he said. "We're like a soccer goalkeeper. We can block 99 shots and nobody wants to talk about any of those. And the only thing anyone wants to talk about is the one that gets through."
Hill later released a statement saying the briefing materials contained a "poor choice of words."
FBI Director Mueller's statement also revealed new details on what the bureau has learned about the Sept. 11 plot. It introduces a financier, Ali Abdul Aziz Ali, who allegedly shifted thousands of dollars before the attacks from the United Arab Emirates to hijackers Mohammed Atta, Marwan al-Shehhi and Nawaf al-Hazmi. His whereabouts are unknown.
Two other chief financiers have previously been named: Mustafa Ahmed al-Hisawi, believed to be bin Laden's financial chief Shaikh Saiid al-Sharif, and Ramzi Binalshibh, an alleged would-be hijacker who was denied access to the United States in 2000. Shaikh Saiid is at-large. Binalshibh was captured in Pakistan on Sept. 11, 2002.
The money trail also links to Khalid Shaikh Mohammed, the alleged operational mastermind of the attacks, Mueller said. But the FBI found no more knowing conspirators in the United States.
"While here, the hijackers effectively operated without suspicion, triggering nothing that alerted law enforcement," Mueller said.
One hijacker, Nawaf al-Hazmi, even reported an attempted street robbery to police in Fairfax, Va., on May 1, 2001, but later declined to press charges, Mueller related. Al-Hazmi's suspected terrorist connections, which date back to 2000, led him to be put on U.S. government watchlists to deny him access to the country on Aug. 24, 2001.
He was already in the country, however, and watchlists weren't applied to those traveling domestically. Three days later, he bought tickets for the flight that crashed into the Pentagon using his own name, Mueller said.