WASHINGTON - Some of the first information gleaned from Osama bin Laden's compound indicates al-Qaida considered attacking U.S. trains on the upcoming anniversary of the Sept. 11 attacks. But counterterrorism officials say they believe the planning never got beyond the initial phase and have no recent intelligence pointing to an active plot for such an attack.

As of February 2010, the terror organization was considering plans to attack the U.S. on the 10th anniversary of the 9/11 attacks. One idea outlined in handwritten notes was to tamper with an unspecified U.S. rail track so a train would fall off the track at a valley or a bridge, according to a joint FBI and Homeland Security bulletin sent to law enforcement officials around the country Thursday.

The al-Qaida planners noted that if they attacked a train by tilting it, the plan would only succeed once because the tilting would be spotted the next time.

The warning, obtained by The Associated Press, was marked for "official use only."

Information on the train plot appears to be the first widely circulated intelligence pulled from the raid this week on bin Laden's secret compound in Pakistan.

After killing the terror leader and four of his associates, Navy SEALs confiscated a treasure trove of computers, DVDs and documents from the home where U.S. officials believe the al-Qaida chief had been hiding for up to six years.

Other intelligence information gathered at the compound represented a terrorist wish list but has revealed no specific plan so far, a U.S. official said. He said documents indicated a desire to hit the U.S. with large-scale attacks in major cities and on key dates such as anniversaries and holidays. But there was no sign those plans were anything more than ambitions. The U.S. official spoke on condition of anonymity to discuss intelligence matters.

Intelligence analysts have been reviewing and translating the material, looking for information about pending plots and other terror connections. Even before the raid, intelligence officials for years have warned that al-Qaida is interested in attacking major U.S. cities on holidays, anniversaries and other dates that are uniquely American.

"While it is clear that there was some level of planning for this type of operation in February 2010, we have no recent information to indicate an active ongoing plot to target transportation and no information on possible locations or specific targets," the warning Thursday said.

The FBI and Homeland Security told local officials to be on the lookout for clips or spikes missing from train tracks, packages left on or near the tracks and other indications that a train could be vulnerable.

Homeland Security spokesman Matt Chandler said, "This alleged al-Qaida plotting is based on initial reporting, which is often misleading or inaccurate and subject to change." He said the government has no plans to issue an official terror alert because of it.

An official with the Association of American Railroads said the organization has received warnings from the federal government and is sharing the information throughout the railroad network. "We are always making sure that the system is run as safely and securely as possible," the organization's spokeswoman, Patricia Reilly, said.

U.S. officials have disrupted other terror plots that targeted rails, including a 2009 plan to blow up the New York City subway system.

On Monday the FBI and Homeland Security warned law enforcement officials around the country that bin Laden's death could inspire retaliatory attacks in the U.S., and terrorists not yet known to the intelligence community could be operating inside the country. The transportation sector - including U.S. rails - remain attractive targets for terrorists.

Associated Press writers Adam Goldman and Matt Apuzzo contributed to this report.

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