From the start of U.S. investigations into the terrorist attacks of Sept. 11, 2001, the question of whether the Saudi government might have been involved has hovered over the case. New evidence has emerged to suggest more strongly than ever that at least two Saudi officials deliberately assisted the first Qaida hijackers. Most of the evidence has been gathered in a long-running federal lawsuit against the Saudi government by survivors of the attacks and relatives of those who died. The court files also raise questions about whether the FBI and CIA, which repeatedly dismissed the significance of Saudi links to the hijackers, mishandled or deliberately downplayed evidence of the kingdom's possible complicity in the attacks. The plaintiffs' account still leaves significant gaps in the story of how two known al-Qaida operatives, Nawaf al-Hazmi and Khalid al-Mihdhar, avoided CIA surveillance overseas, flew into Los Angeles under their own names and then ... settled in Southern California. Still, the lawsuit has exposed layers of contradictions and deceit in the Saudi government's portrayal of Omar al-Bayoumi. FBI agents identified Bayoumi as having helped the two young Saudis rent an apartment, set up a bank account and take care of other needs. Bayoumi, then 42, was arrested on Sept. 21, 2001, in Birmingham, England. After pressure from Saudi diplomats, Bayoumi was freed by the British authorities without being charged. U.S. officials did not try to have him extradited.