One law enforcement source said that an alert issued on Thursday and tied to rail security is the first new notice that can be linked to the early Monday raid on the Abbottabad compound where the al Qaeda leader was found and killed.

That notice says that, in February 2010, al Qaeda members discussed a plan to derail trains in the United States by placing obstructions on tracks, according to a source who received the notice.

The plan was to be executed this fall, on the 10th anniversary of the September 11, 2001, attacks. But no specific city or rail system was identified in the notice, the source said.

Earlier Thursday, a U.S. official speaking to CNN on condition of anonymity said that "valuable information has been gleaned already," though no specific plots or terrorist suspects were identified.

Members of the US special operations unit involved in that raid will meet with President Barack Obama on Friday, a senior administration official said Thursday.

Obama will travel to Fort Campbell in Kentucky on Friday "to privately thank some of the special operators involved in the operation," according to the official.