September 13, 2001 Posted: 9:18 AM EDT (1318 GMT)
WASHINGTON (CNN) -- Federal investigators believe they know the names of the some of those involved in commandeering two airliners out of Boston Tuesday and steered them into the twin towers of the World Trade Center in New York, sources told CNN Wednesday.
The FBI is working on the assumption that there were between 12 ande 24 hijackers directly involved in the attacks, and that there may have been as many as 50 people involved in the planning and execution of the attacks.
Sources also said all the hijackers may not have known one another, to prevent them from giving away information if they were captured and interrogated.
Law enforcement sources said the hijackers may have gone into action, performing pre-assigned roles, on receiving a signal.
Plane tickets for seven people suspected of being the hijackers were purchased with one credit card, information federal investigators deem extremely critical evidence, sources told CNN.
The credit card apparently belonged to a material witness picked up in Boston, not one of the hijackers.
Two of the hijackers apparently came to the United States from Nova Scotia, Canada, crossing the border via a ferry to Bar Harbor, Maine, sources said.
The Royal Canadian Mounted Police and Interpol are assisting U.S. law enforcement in retracing their steps in Canada.
Authorities believe three to five hijackers were on board each of the four planes that crashed Tuesday, sources said.
Two jets slammed into the towers of New York's World Trade Center, one hit the Pentagon, and the fourth crashed in rural Pennsylvania.
Key rental car records
After an initial review of passenger manifests from the flights involved, investigators began looking at several people, including at least one with suspected links to bin Laden, the wealthy Saudi exile living in Afghanistan accused of masterminding the 1998 bombings of two U.S. embassies in Africa.
The four pilots suspected in Tuesday's attack were traced with the help of rental car records from cars left in Maine and Massachusetts.
Evidence found in a rental car left in Portland, Maine, led investigators to two houses in Vero Beach, Florida. One had been rented by two brothers from Saudi Arabia.
Inside the house was a photo of Adnan Bukhari and a pilot's certificate in his name. There was also a pilot's certificate in the name of his brother, Ameer Abbas Burkari. On Thursday, sources close to the investigation said Adnan Bukhari was helping police with their investigation. Ameer Bukhari is believed to have been killed in a light aircraft accident prior to Tuesday's attacks.
The landlord said Adnan Bukhari and another man who lived next door described themselves as Saudi pilots and lived with their wives and children.
Law enforcement sources believe the neighbor may have been one of the hijackers who piloted the plane commandeered from either Newark, New Jersey, or Washington's Dulles International Airport.
The landlord, Paul Stimeling, said the wife and the children of the next door neighbor of Adnan Bukhari moved out over the weekend. The Bukhari family, the landlord said, moved out at the end of August.
Investigators believe the Bukhari brothers died onboard the jetliners involved in the crashes. Law enforcement sources said the FBI is seeking to question the family members as material witnesses.
The two brothers rented a car, a silver-blue Nissan Altima, from an Alamo car rental at Boston's Logan Airport and drove to an airport in Portland, where they got on US Airways Flight 5930 at 6 a.m. Tuesday headed back to Boston, the sources said.
Investigators are analyzing videotapes at the car rental facility and at the Maine airport.
Law enforcement sources said investigators searched the Florida houses for documents pertaining to other students at Flight Safety International, a Vero Beach aviation school.
FBI investigators also obtained the records of student pilots from other flight training schools in the area, including Embry-Riddle University in Daytona Beach and Huffman Aviation International in Venice.
Information found in another rental car left in Boston's Logan Airport -- where two of the hijacked flights originated -- led investigators to two more men who were pilots: Mohammed Atta and Marwan Yousef Alshehhii.
The two men held passports from the United Arab Emirates. A Florida driver's license was issued to Atta on May 2, 2001, and he previously held an Egyptian driver's license.
Federal investigators said both men received training at Huffman Aviation International.
The Mitsubishi sedan sources said was rented by Atta, contained materials written in Arabic, including flight manuals, that law enforcement sources called "helpful" to the investigation.
An apartment linked to Atta was searched in Coral Springs, Florida. Investigators also said they are checking the phone records of each of the addresses searched. They are also attempting to obtain fingerprint and DNA samples, sources said.
Lookout alerts and talking witnesses
Police issued a lookout alert for two cars -- a 1989 two-door red Pontiac with the license plate D79-DDV or DVD and a four-door Oldsmobile with the license plate VEP-54N. A vehicle registration record obtained by CNN showed the Pontiac was registered to Atta.
Heavily armed police and FBI agents swarmed the Westin Hotel in the Copley Square area of Boston Wednesday. Sources said three people were taken into custody as material witnesses. Others were picked up in Florida.
The individuals have not been arrested and they have not been described as suspects, but authorities said they could provide "important material information" related to the attacks.
Said one source: "They are talking."
A source said two of them may have "immigration status problems." Law enforcement sources said a cell has been operating for more than a year in the Springfield and Worcester areas, west of Boston.
Other developments
In Hamburg, Germany, the BKA, the federal criminal agency, searched one apartment at the request of the FBI, a police spokesman said Wednesday.
He said agents found that one of the apartments has been empty since February and the resident of the other did not match the name given by the FBI, so the second apartment was not searched.
Agents are taking evidence samples from the apartments, the spokesman said.
In another development, law enforcement sources said the United States intercepted two phone calls after the Tuesday attacks between members of al Qaeda, the terrorist network sponsored by suspected terrorist bin Laden.
In those conversations, the individuals discussed hitting two targets, the sources said.
In still another development, sources told CNN that America Online turned over records of e-mails Wednesday for the accounts belonging to the suspected hijackers.
-- CNN Correspondents Mike Boettcher in Atlanta, Kelli Arena, Eileen O'Connor in Washington, Susan Candiotti in Florida and Boston Bureau Chief Bill Delaney contributed to this report.