Filed at 2:35 p.m. ET

WASHINGTON (AP) -- Federal authorities are investigating whether four separate cells of terrorists were involved in Tuesday's devastating attacks. At least one set of hijackers is believed to have crossed from Canada and had ties to Osama bin Laden, law enforcement officials said Wednesday.

FBI agents obtained information from Internet providers, conducted searches, and questioned people in Florida and Massachusetts. Early evidence indicated the attacks were tied to the wealthy Arab and accused terrorist, including communications among bin Laden supporters.

But officials cautioned the information, including raw intelligence, was still developing. No significant arrests were made as of midday Wednesday.

``This could have been the result of several terrorist kingpins working together. We're investigating that possibility,'' one law enforcement official told The Associated Press.

Added another official: ``The evidence suggests these cells each operated the same way at the same time but we don't know yet whether each knew of the other's activities.''

Officials said authorities were gathering evidence that the four terrorist cells may have had prior involvement in earlier plots against the United States, including the USS Cole bombing and the foiled attack on U.S. soil during the millennium celebrations.

The officials, who spoke on condition of anonymity, said they were investigating whether one group of hijackers crossed the Canadian border at a checkpoint and made their way to Boston, where an American Airlines flight was hijacked and flown into the World Trade Center in New York.

The officials confirmed a car believed to belong to the hijackers was confiscated in Boston and contained an Arabic language flight manual.

Law enforcement officials said two hotel rooms in the Boston area believed to have been used by the hijackers were searched by the FBI Wednesday afternoon. The officials found information linked to a name on the manifest of one of the hijacked flights. They declined to identify the man.

A Venice, Fla., man said FBI agents told him that two men who stayed in his home while training at a local flight school were the hijackers. Charlie Voss said the agents identified the men as Mohamed Atta and one known as Marwan.

The government believes the hijackers were trained pilots and that three to five were aboard each of four airliners that crashed in the worst terrorist attack ever in the United States, said Justice Department spokeswoman Mindy Tucker. She said the conclusion was based on information gathered from frantic phone calls made by passengers on the doomed jets.

``It appears from what we know that the hijackers were skilled pilots,'' said Tucker.

The FBI in Miami issued a national bulletin for law enforcement agencies to look out for two cars. Records with the Florida Division of Motor Vehicles show that one of the vehicles the FBI was pursuing -- a 1989 red Pontiac -- was registered to Atta.

The FBI has already received more than 700 tips from a special Web site seeking information on the attacks.

Agents served search warrants on major Internet service providers in order to get information about an e-mail address that may be connected to Tuesday's terrorist attacks. Among those who received warrants was Earthlink, officials said.

AOL, the nation's largest provider, said it will comply with requests quickly.

The FBI interviewed Voss, of Venice, Fla., about two men who stayed with him and his wife for a week in July 2000 while taking small-plane flight training at the municipal airport.

FBI agents ``informed me that there were two individuals that were students at Huffman Aviation, my employer, and FBI told me they were involved in yesterday's tragedy,'' Voss said.

The couple accepted the two men as house guests as a favor to the company, Voss said. The men, who stayed just a few days, trained at the airport and came to the house to sleep, he said.

Tucker declined to comment on evidence linking the attacks to bin Laden or whether authorities have executed search warrants.

Lawmakers, including Sen. Orrin Hatch, R-Utah, believe bin Laden may have been behind the attacks. ``I don't think everyone in Congress has enough information to make those assumptions,'' Tucker said.

She said investigators are following all credible leads, but declined to comment on whether the government is close to arresting anyone. The 700 tips came from a special FBI Web site seeking information on the attacks.

From broken bits of hijacked airplanes to intelligence intercepts, the FBI is collecting evidence in its search for those responsible for the attacks. At the Pentagon, an FBI team recovered parts of the airplane's fuselage and sought the black box recorder that could provide conversations from the cockpits of the doomed planes.

``Everything is pointing in the direction of Osama bin Laden,'' said Hatch, the top Republican on the Senate Judiciary Committee.

A flight manifest from one of the ill-fated flights included the name of a suspected bin Laden supporter, Hatch and several law enforcement officials confirmed. And U.S. intelligence obtained communications between bin Laden supporters discussing Tuesday's attacks on the World Trade Center in New York and the Pentagon, Hatch said.

``They have an intercept of some information that included people associated with bin Laden who acknowledged a couple of targets were hit,'' he said. Hatch declined to be more specific.