Mohamed Atta, suspected ringleader of the Sept. 11 terrorist hijackings, rented rooms in New York City in the spring of 2000 with another hijacker, a federal investigator said.

Authorities learned of their stay in New York while retracing the hijackers' steps prior to the attacks, according to the investigator, who spoke to The Associated Press on condition of anonymity.

Investigators confirmed that Atta and the second man rented rooms in Brooklyn and the Bronx, and are trying to identify anyone who might have supported them.

Atta's trail in Brooklyn began with a parking ticket issued to a rental car he was driving, said a senior Justice Department official, who also spoke on condition of anonymity.

"We know a lot since Sept. 11," the official said. "We know how (the hijackers) came in and where they were. But there's still a lot of pieces we don't know."

Neither official would elaborate on Atta's activities in New York or identify the hijacker who accompanied him.

Marwan Al-Shehhi, a hijacker believed to be a relative of Atta, entered the United States at about the same time. Atta and Al-Shehhi are believed to have been at the controls of the planes that hit the World Trade Center.

Atta, an Egyptian with ties to Islamic fundamentalists in Germany, flew to Newark, N.J., on June 2, 2000 from Prague in the Czech Republic, Czech authorities have said. The trip is his earliest confirmed visit to the United States.

By July 2000, Atta and Al-Shehhi were taking pilot lessons at a flight school in Venice, Fla.

Atta has emerged as a central figure among the hijackers. In the months before the terror attacks he was seen in Florida, Maryland, New Jersey, California and Nevada with the men who went on to hijack four jetliners on Sept. 11. He also made at least three trips to Europe between June 2000 and Sept. 11, once meeting with a suspected Iraqi intelligence agent.

Unlike others who used stolen identities to confuse authorities, Atta mostly used his own name and vital statistics as he traveled the country in the months before the hijackings.

Witnesses have identified Atta as a frequent visitor at a Paterson, N.J., apartment rented by other hijackers six months before the attack. He also was seen in a suburban Washington motel room where five men stayed from late August through Sept. 10.

On Sept. 10, Atta and another hijacker, Abdulaziz Alomari, checked into a motel in Portland, Maine. The next morning, they flew to Boston, where they barely caught American Airlines Flight 11. That jetliner crashed into the World Trade Center.