Parts of the report refer to the warnings President Bush received about a possible attack and secrecy cloaking budget decision on anti-terrorism funds, The Washington Post reports. Some areas of Clinton-era policy were also kept secret.
The 900-page report released Thursday, a result of the 10-month investigation last year by the House and Senate intelligence committees, found that U.S. intelligence agencies had no "smoking gun" — no single piece of evidence that pointed specifically to the impending Sept. 11 attacks.
But it also concluded that important clues had been ignored, information had not been shared among agencies and inadequate attention was paid to the likelihood of a major domestic terrorist attack.
According to the report, the "best chance to unravel the Sept. 11 plot" was lost because intelligence agencies failed to let the San Diego FBI office know that two men were suspected terrorists — and would later turn out to be among the hijackers.
But it also opens important questions on the White House role.
One tidbit concerns President Bush's Aug. 6, 2001 daily briefing. Previously, national security adviser Condoleezza Rice said the briefing was "analytic," profiling Osama bin Laden, and not a warning.
But the report released Thursday indicates the briefing included information "acquired in May 2001 that indicated a group of Bin Laden supporters was planning attacks in the United States with explosives." It referred to an al Qaeda support base in the United States, and FBI "judgments about patterns of activity consistent with preparations for hijackings or other types of attacks."
The CIA and White House refused to make the briefing paper itself available. The White House Office of Management and Budget, meanwhile, declined to reveal who in the administration was responsible for not increasing the nation's counterterrorism budget.
Much of the report's information about whether the Saudi government offered any help to the hijackers was also kept secret. But the report included criticism of Saudi cooperation in fighting terrorism. Fifteen of the 19 hijackers were Saudis.
Prince Bandar bin Sultan, the Saudi ambassador to the United States, responded in The Post: "It is unfortunate that false accusations against Saudi Arabia continue to be made by some for political purposes despite the fact that the kingdom has been one of the most active partners in the war on terrorism."
As CBS News Correspondent Jim Stewart reports, the report raises many "what if" scenarios involving the CIA, FBI, INS and other government departments.
Some of the strongest clues centered on two hijackers, Khalid al-Mihdhar and Nawaf al-Hazmi.
They were identified after attending an al Qaeda meeting in Malaysia in January 2000, but information about them was not widely shared in the intelligence community. They were not placed on a State Department watch list until weeks before the attacks and, until then, were able to freely enter and leave the United States.
The two men had "numerous contacts" with an FBI informant in San Diego, but the agent responsible for the informant did not know they were suspected terrorists.
The agent told congressional staff that if he had known "we would have done everything. We would have used all available investigative techniques. We would have given them the full-court press."
Also, FBI and Treasury financial crime officials said they would have been able to locate the two hijackers in August 2001 through credit card and bank information.
Al-Mihdhar and al-Hazmi received "considerable assistance" from Omar al-Bayoumi, who is identified as having ties to al Qaeda and also was identifed by one of the FBI's best sources as likely an intelligence officer for Saudi Arabia or a foreign power.
The report said that in May 2001, the suspected mastermind of the attacks, Khalid Shaikh Mohammed, was identified in an intelligence report as seeking recruits to travel to the United States for terrorist activities. Those individuals would be expected to make contact with "colleagues" already there, it said.
The report also detailed intelligence reports that warned of possible al Qaeda attacks. One warning received in December 1998 said "plans to hijack U.S. aircraft proceeding well" and two individuals "had successfully evaded checkpoints in a dry run at a NY airport." The source of the warning was not identified.