SAN DIEGO -- Numerous contacts between two hijackers and a longtime counterterrorism informant in San Diego could have given the FBI's San Diego office "perhaps the intelligence community's best chance to unravel the Sept. 11 plot," according to the final report of a congressional inquiry.

The massive report released Thursday also says that the hijackers dealt with others who emerged on the FBI's radar screen during investigations of radical Islamic extremists, including Omar al-Bayoumi, a Saudi who an FBI source believed to be a spy.

The 850-page report shows that wide-ranging parts of the nation's intelligence and law enforcement apparatus detected threads that were only later connected to the hijacking plot.

The report concludes that nowhere did the government possess the long-sought "smoking gun" -- specific information that told officials where, when and how the attacks would come, the report concludes.

But it had enough pieces to begin to unravel the plot, had it put them all together.

FBI officials in San Diego insisted that they did not have enough information to thwart the attacks on the World Trade Center and the Pentagon.

"Even in the bright light of hindsight there simply wasn't a road map to Sept. 11," said Daniel R. Dzwilewski, the special agent who took charge of the FBI's San Diego bureau three weeks ago.

Hijackers Nawaf Alhamzi and Khalid Almihdhar, who were aboard American Airlines Flight 77 when it crashed into the Pentagon, rented rooms in 2000 at the Lemon Grove home of Abdussattar Shaikh, a local professor identified in news reports as the FBI informant.

Shaikh phoned The Associated Press and denied being an informant before hanging up. The report says that the San Diego FBI concluded that the informant had no knowledge of, or role in, the Sept. 11 plot, but notes that he made numerous inconsistent statements that call his credibility into question.

Steve Butler, a former San Diego FBI agent who was the informant's contact, testified before the congressional panel that he learned the names of the two hijackers only in a passing conversation during the summer of 2000.

Butler lamented the CIA's failure to pass along that the two hijackers had been identified after attending an al-Qaida meeting in Malaysia in January 2000.

"It would have made a huge difference," said Butler, who retired last year. "We would have done everything. We would have used all available investigative techniques. We would have given them the full-court press."

FBI officials in San Diego say the hijackers, due to their limited English skills, were instructed to pose as students and rely on local Muslims to help them blend in. They did so with help from al-Bayoumi and others linked to "terrorist elements," according to the report.

Al-Bayoumi found the pair an apartment, paid their first month's rent and security deposit and threw a welcoming party for them. Although he was a student in San Diego, the report states al-Bayoumi had access to "seemingly unlimited funding from Saudi Arabia," including $400,000 to fund a Kurdish mosque in the city.

In January 2000, al-Bayoumi had a closed-door meeting at the Saudi consulate in Los Angeles and then went to a restaurant where he picked up Alhazmi and Almihdhar and brought them to San Diego. One of the San Diego FBI's best sources believed that al-Bayoumi "must be an intelligence officer for Saudi Arabia or another foreign power."

The FBI says its investigation found no signs that a foreign government was behind the Sept. 11 attacks.

According to the report, al-Bayoumi also had ties to al-Qaida, but an extensive investigation after the Sept. 11 attacks resulted in no criminal charges, and he is now living in Saudi Arabia.

New information emerged in the report about the owner and manager of a San Diego business that employed Alhazmi in 2000. Both men were on the FBI's radar. The business is not named, but Alhazmi briefly worked at a Texaco gas station in La Mesa.

The business owner, a U.S. citizen whose name does not appear in the report, told a San Diego police officer during a 1991 traffic stop that "all Americans should be killed for what they did to the Iraqis" during Desert Storm and "that the United States needed another Pan Am 103 attack and that he would be the one to carry it out."

In 2001, the man's stockbroker called the FBI to say the business owner had closed his account and was sending the money to freedom fighters in Afghanistan.

The manager of the business also had connections that caught the FBI's attention. In January 2000, the brother of a known member of Osama bin Laden's terrorist network got into the manager's car in a Los Angeles parking lot.

After the Sept. 11 attacks, the manager said he hired Alhazmi on the recommendation from a nearby mosque.

An imam at the Masjid Ar-Ribat al-Islami mosque served as "spiritual adviser" to the two hijackers in San Diego. When the imam moved to Falls Church, Va., in 2001, the hijackers moved there as well. The imam is not named in the report, but sources told The Washington Post he is Anwar Aulaqi, a Yemeni who left the United States last year.

The FBI opened a counterterrorism inquiry into the imam in June 1999 for reasons that are omitted from the report. The next year, the imam was visited by an associate of Sheik Omar Abdel Rahman, the blind cleric who is serving a life sentence for conspiring to blow up New York City landmarks and assassinate Egyptian President Hosni Mubarak.