Updated

No single piece of information could have prevented the Sept. 11 terrorist attacks, not even an FBI informant who became acquainted with two of the hijackers, a congressional report says.

The unidentified informant was with Khalid Almihdhar and Nawaf Alhazmi in San Diego during the summer of 2000 but never suspected they were terrorists, the report said.

Almihdhar and Alhazmi recently had been linked by U.S. intelligence officials to possible terrorist activity, but that information apparently had not been shared with the FBI, the report said. Nothing the two men said or did in the presence of the informant aroused suspicion.

Almihdhar and Alhazmi were aboard American Airlines Flight 77 (search), which crashed into the Pentagon. The informant also may have been introduced to Hani Hanjour, who U.S. officials believe piloted that hijacked plane.

Before the attacks, Almihdhar and Alhazmi were boarders in the home of Abdussattar Shaikh, a native of India and retired educator known as a devout Muslim who regularly invited young students to stay at his home.

The informant's role in the months leading up to the Sept. 11, 2001, attacks is among new details that emerge from the 900-page declassified version of last year's report by the House and Senate intelligence committees.

Portions of the report, scheduled for release Thursday, were described Monday to The Associated Press by law enforcement officials on condition of anonymity.

Blacked out in the report is a 28-page section that the officials say criticizes Saudi Arabia's government and details its lack of interest in tackling Muslim extremism.

The report finds no single piece of intelligence or information that could have stopped the attacks, stating at one point: "The joint inquiry did not uncover a smoking gun."

Instead, officials say the blame is spread across the federal government, from the failure by the CIA (search) and other intelligence agencies to share information to the failure by the FBI (search) to focus attention on a burgeoning terrorist threat inside U.S. borders.

"There's a lot of shared failure and blame to go around," said former Rep. Tim Roemer, D-Ind., who was a member of the joint intelligence panels that conducted the inquiry.

Newsweek magazine first revealed the report's information about the informant. According to federal enforcement officials, the informant reported contact with Almihdhar and Alhazmi to his FBI handler in the summer of 2000. The report said he gave only their first names, and there was no reason for the men to have caused misgivings since at that point neither was on government watch lists of suspected terrorists.

It wasn't until after the October 2000 bombing of the USS Cole (search) at port in Yemen that the FBI learned both men had attended a January 2000 meeting in Malaysia of major Al Qaeda operatives. The CIA had known the two attended the meeting, but apparently the information never was shared with the FBI.

It took until Aug. 23, 2001, three weeks before the attacks, for their names to be placed on lists of suspected terrorists that would have prevented them from entering the United States or allowed their arrest and detention had they tried to leave.

Without their appearance on those lists, the FBI had no way of telling its San Diego informant of suspicions about them. So the informant never was asked to collect intelligence about them, the report said.

After the attacks, the informant cooperated with the FBI and passed a polygraph test about his contacts with the hijackers. His name and location remain secret, and the FBI refused congressional requests last fall for the informant to testify on Capitol Hill.

Since the attacks, the government has overhauled the way suspected terrorists are tracked, clamped down on entry and exit rules and moved to encourage sharing of information by the CIA and FBI.

The report also details the role played in San Diego by Omar al-Bayoumi, a student with links to officials at the Saudi Arabian consulate in Los Angeles. A reliable FBI source, the report said, told U.S. agents that al-Bayoumi "must have been an intelligence officer for Saudi Arabia (search) or another foreign power."

The U.S. government has frequently criticized the Saudi government for not doing more to curb terrorism and, especially, to cut off terrorist groups' financial sources. U.S. officials recently have praised Saudi cooperation in the investigation of an attack in the Saudi capital, Riyadh, last May that killed 35 people including nine Americans and nine Saudi suicide bombers.

Al-Bayoumi, the report said, met Almihdhar and Alhazmi in Los Angeles, directed them to a Muslim community in San Diego and even wrote a check for their apartment deposit. An extensive investigation into al-Bayoumi after the Sept. 11 attacks resulted in no criminal charges, and he is now living in Saudi Arabia.