WASHINGTON (AP) -- The FBI released photos Thursday of the 19 suspected suicide hijackers with a plea for citizens to help with identities of some that are still in doubt. Director Robert Mueller said some attackers had been linked to Osama bin Laden's network.
Separately, more arrests were made of Middle Eastern men who obtained bogus licenses to haul hazardous materials. The FBI said those men were not connected to the hijackers, who crashed planes into the World Trade Center and the Pentagon.
The FBI isnOt certain about the identities of all the hijackers.
"It is our hope that the release of these photos will prompt others who may have seen the hijackers to contact the FBI with any information they may have that would be helpful to the investigation," said Attorney General John Ashcroft.
The release of the photos, which come from passports, driver's licenses and other documents identified with the hijackers, marked a change for authorities, who until now have kept them under wraps so that potential witnesses and others shown the photos get a fresh look at the men.
Mueller said the FBI believes the names and photographs match those on the manifests of the hijacked planes. But questions remain about whether those are the true names of the hijackers.
"What we are currently doing is determining whether, when these individuals came to the United States, these were their real names or they changed their names for use with false identification in the United States," said Mueller.
He said there was evidence that one or more of the hijackers had had contacts with al-Qaida, the network associated bin Laden. He declined to be more specific.
In other developments:
--An Arabic-language document containing prayers and spiritual references that was found at the Pennsylvania crash site of United Flight 93 is believed to have been used by the hijackers to prepare for their mission to bring the plane down, said a government official, speaking on condition of anonymity.
--A grand jury in Boston investigating terrorism subpoenaed student records from the University of Rhode Island. It was among several universities that have received subpoenas from grand juries in the investigation. "Our belief is it's a general request," University of Rhode Island spokeswoman Linda Acciardo said. "We have no reason to believe it's connected to the individuals who hijacked the planes." The university said it learned the subpoena was related to the attacks after it contacted the FBI in Boston to confirm it, she said.
--Evidence surfaced in Las Vegas that at least five of the hijackers had stayed in the casino city between May and August, said a source who insisted on anonymity.
--A provider of instant message services said two employees of the firm received text messages warning of an attack on the United States two hours before the terrorists struck. Avner Ronen, vice president for strategic development at Odigo Inc., said that the warning was "general, not specific" and that the sender of the instant message was not known to the Odigo employees. The FBI is investigating. The online news service Newsbytes reported that the Odigo employees recorded the Internet protocol address of the message's sender, which could facilitate tracing the message to its origin.
Regarding the FBI's list of 19 hijackers, some of the names have slightly different spellings and others have additional names added, compared with the list released by the FBI on Sept. 14.
At least four of the identities released Sept. 14 have been challenged by people with the same or similar names.
Saudi Arabia Embassy officials, for example, have said that a Saudi electrical engineer named Abdulaziz Alomari -- the same name as one of the alleged hijackers on the plane that crashed into the Pentagon -- had his passport and other papers stolen in 1996 in Denver when he was a student, and reported the theft to police there at the time.
The FBI director said there was some evidence that "one or more" of the hijackers was related.
Amid fears that terrorists could strike with chemical or biological weapons, investigators continued to scour the country for individuals who unlawfully obtained licenses to drive trucks hauling hazardous materials.
Twenty Middle Eastern men have been charged with obtaining bogus licenses; 18 were arrested Wednesday and Thursday and two were still at large, officials said.
Mueller said the 20, charged in a license scam uncovered in Pennsylvania, have not been linked to the Sept. 11 attacks but investigators are looking for people who have obtained licenses "under suspicious circumstances."
"We're under a heightened state of alert," said Mueller.
Meanwhile, in Detroit, a federal grand jury indicted three men, including two arrested last week at a Detroit house. The third man's alias, Jalali, appeared on documents found when agents searched the house.
Authorities also found a planner with Arabic writing that gave information about an American base in Turkey, the "American foreign minister" and what appeared to be a diagram of an airport flight line.
The whereabouts of Jalali, whose name is Youssef Hmimssa, are unknown, according to Gina Balaya, spokeswoman for the U.S. Attorney's office.
Karim Koubriti, 23, Ahmed Hannan, 33 and Youssef Hmimssa were charged with two counts: fraud and misuse of visas, permits and other documents, and fraud in connection with identity documents and information.
Agents went to the home searching for Nabil Al-Marabh, on the agency's watch list in its terrorism investigation. Marabh was arrested last week outside of Chicago. Records show he holds a truck driver's license and is certified to transport hazardous materials.
Police in Toronto searched three residences and a business linked to Al-Marabh.