In Washington, State Department officials said they have intelligence information that connects the attacks on the twin towers in New York and on the Pentagon to Saudi millionaire dissident Osama bin Laden. The leads being developed in Boston, Maine and Florida seem to point in the same direction.
In Boston, the FBI has identified five suspects, at least two of whom flew from Portland, Maine, to Logan airport on Tuesday morning. In Florida agents are focusing on several people believed to have ties to bin Laden.
In Maine, authorities have impounded a car found at the Portland International Jetport, according to Steve McCausland, the spokesman for the state Department of Public Safety.
The blue Nissan Altima was towed away and taken to the state police crime lab in Augusta at around 3 a.m. today, four hours after it was discovered, McCausland told ABCNEWS.com, but he declined to comment on what led FBI and state police to focus on the car. The Associated Press said the car had been rented.
Maine Gov. Angus King told the AP that the evidence police and the FBI were gathering in the state "appears to open a series of leads that I'm sure will help to identify who the attackers [were]."
The FBI has determined there were three hijackers on the plane that took off from Dulles International Airport and later crashed into the Pentagon, and investigators know their names, sources said.
The evidence gained in the first 24 hours of the investigation points to a highly organized operation, with at least four of the terrorists having some training in flying commercial aircraft. Among the evidence found in both Boston and Florida were flight training materials.
Cell phone calls from passengers on three of the flights also indicate that the hijackers attacked the flight crew and passengers, likely to create a disturbance that would draw the pilots out of the cockpit and allow the terrorists to gain access to the controls.
Terrorists Studied Logan Security
The Boston Globe reported that the bags of one of the two men who flew in to Boston from Portland did not make the connection to the plane that was hijacked, and the luggage contained a copy of the Koran, an instructional video on flying commercial airliners and a fuel consumption calculator.
At about 9 p.m. Tuesday, FBI agents and Massachusetts State Police towed a late model white Mitsubishi Mirage with a Virginia license plate to an FBI garage where investigators would go over it with a fine-toothed comb for evidence. The car had been rented, according to an airport official.
A report in the Boston Herald, said the car contained Arabic-language flight training manuals.
Investigators were led to the car by another airline passenger who got into a dispute with two men in the car over a parking space. When he heard about the planes that crashed into the World Trade Center, he called authorities in Boston and told them about the incident Tuesday morning.
It is believed that the two men entered the United States from Canada.
Logan airport officials defended security at the airport in a news conference Tuesday night, but law enforcement sources today said that it appears that those responsible for the hijacking had cased the airport, making several trips back and forth between Portland and Boston.
A large contingent of FBI agents were sent to Portland to investigate suspicions that a cell of bin Laden followers could be operating in that city.
Seeking a Suspect in Florida
In Florida, FBI agents searched a home in Davie where they believed a man named Mohammed Acca lived, but it turned out he had never resided in the house.
Agents are also looking for two cars — a tan four-door Oldsmobile Aero that was traced to a leasing company in Boca Raton, Fla., and a red two-door 1989 Pontiac Grand Prix that has been traced to Acca, sources said.
Agents are also following up leads related to a car in which a picture of bin Laden was found, along with flight training manuals. The car belonged to a former student at Embry Riddle University, a highly respected aeronautical and aviation school.
Sources said that the FBI may have been seeking search warrants in Daytona Beach and Venice, Fla.
The FBI was led to Florida by information gained from studying the flight manifests of the four planes that were hijacked.
Nothing Out of the Ordinary
In Boston, the FBI is being assisted in its investigation by 150 state police detectives, and dozens of FBI agents who were brought to the city from New York to help.
Among the bags of evidence gathered from the airport were two chairs that it was believed the two men sat in while they waited for their flight, which was scheduled to go to Los Angeles. Investigators hope to get DNA from the seats.
Investigators interviewed ticket takers who may have been the last people to come into contact with the hijackers before they boarded the flights.
"They asked me if I saw anything out of the ordinary, but it would have been something I would have called to my manager's attention if I would have seen it at the moment," said one of the ticket takers, Gismond Pepin.
"Unfortunately, nothing caught anybody's eye that was suspicious," she added.
In East Rutherford, N.J., three men were taken into custody late Tuesday after being pulled over on Route 3. The police were looking for them because they had been seen celebrating at Liberty State Park after the planes hit the World Trade Center.
The Bergen County Bomb Squad searched their van and found no explosives, but the three men and the van were turned over to the FBI.
Claims of Responsibility
There were conflicting reports of groups claiming or denying responsibility for the attacks, beginning soon after they occurred.
An Abu Dhabi television station reported that a militant Palestinian group had claimed responsibility, but the group later denied any involvement.
Bin Laden, wanted for his suspected role in the attack on the USS Cole and two U.S. embassies in Africa, reportedly denied his al Qaeda network was involved in the attacks.
The Pakistani newspaper Khabrain quoted bin Laden as saying, "The terrorist act is the action of some American group. I have nothing to do with it."
In the United States, though, attention is focused on bin Laden, according to Sen. Orrin Hatch, R-Utah, ranking member of the Senate Judiciary Committee.
Hatch told ABCNEWS that "top people at the CIA" told him "just about everything points in the direction of Osama bin Laden. He said that there was already evidence suggesting that bin Laden associates were on at least one of the hijacked aircraft. 