In Florida yesterday, FBI agents were interviewing three Saudi Arabian flight engineers who are taking classes at Flightsafety International’s flight school in Vero Beach, Fla., said company spokesperson Roger Ritchie.

The school does not have simulators for Boeing 767 and 757 aircraft such as the ones involved in Tuesday’s attacks, Ritchie said.

Investigators who spoke to the Associated Press on condition of anonymity said that multiple cells of terrorist groups participated in the coordinated operation and the hijackers had possible ties to several Middle Eastern countries.

Investigators were gathering evidence that the terrorist cells may have had prior involvement in earlier plots against the United States, and may have been involved with Saudi exile Osama bin Laden—including ties to the bombing of the U.S.S. Cole bombing in a Yemenite harbor last fall and the foiled attack on Los Angeles airport during the millennium celebrations.

Secretary of State Colin L. Powell yesterday named bin Laden as a prime suspect in engineering Tuesday’s terrorist attacks.

—Material from Associated Press reports was used in the compilation of this article.

—Staff writer Garrett M. Graff can be reached at ggraff@fas.harvard.edu.