The FBI issued a warning to state and local law enforcement nationwide Thursday about a possible attack soon against transportation systems, particularly railroads.

Officials said the warning, based on information obtained from Al Qaeda prisoners, suggested that terrorists may try to take out bridges, key sections of tracks or train engines in an effort to cause derailments and widespread damage.

"Information from debriefings of Al Qaeda detainees as of mid-October indicates that the group has considered directly targeting U.S. passenger trains, possibly using operatives who have a Western appearance," the FBI said in a statement.

Intelligence officials continue to believe that Al Qaeda plans to attack targets that would be readily recognized as representing U.S. economic interests, the FBI said.

Captured Al Qaeda photographs of U.S. railroad engines, cars and crossings have increased concern about the threat, the FBI said.

Amtrak President David Gunn said federal transportation officials notified him about the warning. "The threat, like a lot of others, is not specific," Gunn said. "It's not targeted at anything per se."

Gunn said the passenger railroad is taking steps to enhance security and passenger safety, but declined to describe them except to say they will not be evident to riders.

Amtrak has increased patrols and freight railroads have tightened security, the FBI said.

Around the Sept. 11 anniversary, Amtrak announced it intended to enforce tighter identification requirements, including random ID checks of passengers on trains. But Amtrak decided to reconsider that plan and has never implemented it.

Edward R. Hamberger, president of the Association of American Railroads, said the nation's rail system won't be a soft target. Since the terrorist attacks, railroads developed a security plan that includes a round-the-clock operations center linking railroad control centers with law enforcement agencies and increased surveillance.

The Office of Homeland Security was contacting key state and local officials to urge their help and vigilance in warding off any such attack, spokesman Gordon Johndroe said.

"The American people should still ride our nation's rails and know that this warning has been provided to state and local law enforcement, and the appropriate security officials, so they can take the appropriate steps to increase protective measures," Johndroe said.

New York Gov. George Pataki said, "There are threats and those out there who are looking to do us harm here in the United States."

He said Ridge did not identify any specific target in New York. Even so, Pataki said, New York has "put out an advisory across the state to make sure that the public is vigilant and we are vigilant in protecting public services and infrastructure points across this state."

Separately, U.S. intelligence has learned that Al Qaeda supporters may be planning strikes on ships in the Persian Gulf and nearby seas, said one official, speaking on the condition of anonymity.

"Such attacks may be a part of more extensive operations against port facilities and other energy-related targets including oil facilities and nuclear power plants," the FBI said.

The threats are to military vessels and commercial shipping, the official said. Terrorists believed linked to Al Qaeda attacked an oil tanker off the coast of Yemen earlier this month.

Johndroe said the homeland security office is coordinating an interagency effort to increase protection of possible targets.