Some of the first information gleaned from Osama bin Laden's compound indicates al Qaida considered attacking US trains on the upcoming anniversary of the September 11 attacks.
But counter-terrorism 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 organisation was considering plans to attack the US on the 10th anniversary of the 9/11 attacks.
One idea outlined in handwritten notes was to tamper with an unspecified US rail track so that a train would derail at a valley or a bridge, according to a joint FBI and Homeland Security bulletin sent to law enforcement officials around the country.
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.
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, US Navy Seals confiscated a treasure trove of computers, DVDs and documents from the home where 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 US official said.
He added that documents indicated a desire to hit the US 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.
Intelligence analysts have been reviewing and translating the material seized at bin Laden's hideout, looking for information about pending plots and other terror connections.