WASHINGTON (AP) - Federal authorities have identified more than a dozen hijackers of Middle Eastern descent in Tuesday's bombings and gathered evidence linking them to Osama bin Laden and other terrorist networks, law enforcement officials said.
The massive investigation stretched from the Canadian border, where officials suspect some of the hijackers entered the country, to Florida, where some of the participants are believed to have learned how to fly commercial jetliners before the attacks. Locations in Massachusetts and Florida were searched for evidence.
The names of two men being sought by authorities emerged in Florida. There, the FBI interviewed a family that gave them temporary shelter a year ago.
The officials, speaking on condition of anonymity, told The Associated Press that multiple cells of terrorist groups participated and that hijackers had possible ties to countries that included Saudi Arabia and Egypt.
The identities of more than a dozen of the men who hijacked four planes with knives and threats of bombs has been ascertained, the officials said. Several hijackers had pilot's licenses.
At least one hijacker on each of the four planes was trained at a U.S. flight school, said Justice Department spokeswoman Mindy Tucker. The flight schools were in Florida and at least one other state. The hijackers used both cash and credit cards to purchase their plane tickets and hotel rooms.
Authorities detained at least a half dozen people in Massachusetts and Florida on unrelated local warrants and immigration charges and were questioning them about their possible ties to the hijackers. No charges related to the attacks had been filed.
Search warrants were executed in Florida, New Jersey and Massachusetts. Sealed warrants went out in several other states, officials said.
''We're attempting to recreate the travels of each of the hijackers on the planes - either the hijackers themselves or their associates,'' FBI Director Robert Mueller said.
For some of the suspected accomplices, ''we have information as to involvement with individual terrorist groups,'' Mueller added. He declined to say which groups or whether they were connected to bin Laden.
Officials said authorities 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 bin Laden. That includes the USS Cole bombing in Yemen and the foiled attack on U.S. soil during the millennium celebrations.
''This could have been the result of several terrorist kingpins working together. We're investigating that possibility,'' one law enforcement official speaking on condition of anonymity told The Associated Press.
Sen. Charles Grassley, the top Republican on the Senate Finance Committee, said the briefing he received Wednesday from law enforcement left him with the same impression.
''Most of it today points to bin Laden but the speculation at the end of the road is that he and his network were very much involved with Hezbollah, Fatah and other'' terrorist organizations, Grassley said.
The senator said authorities told him all the hijackers were of Middle Eastern descent and that they had ''a tremendous amount of ground support for each hijacker.''
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 involved in the attacks. Charlie Voss, a former employee at Huffman Aviation in Venice said the FBI told him one of men was named Mohamed Atta. A student at Huffman Aviation identified the second man as Marwan Alshehhi.
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, who previously had a driver's license in Egypt.
Attorney General John Ashcroft said numerous promising leads were being followed up. ''The Department of Justice has undertaken perhaps the most massive and intensive investigation ever conducted in this country,'' he said.
Ashcroft said authorities were conducting interviews and reviewing airline manifests, rental car records and pay phone records. He said between three and six hijackers, armed with knives and box cutters, seized control of the four commercial jets. Two hit New York's World Trade Center, a third smashed into the Pentagon and a fourth crashed in Pennsylvania.
Some 4,000 special agents and 3,000 support personnel are assisting in the investigation, and 400 FBI laboratory specialists are at the crime scenes in New York, Washington and Pennsylvania.
Evidence has been collected at the Pentagon and Pennsylvania site, but investigators have not yet been able to start work at the World Trade Center, where the search for survivors continued.
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.