Washington:
After reviewing computer files and documents seized at the compound where Osama bin Laden was killed, American intelligence analysts have concluded that the chief of Al Qaeda played a direct role for years in plotting terror attacks from his hide-out in Abbottabad, Pakistan, United States officials said Thursday.
The C.I.A. had Bin Laden's compound under surveillance for months before American commandos killed him in an assault on Monday, watching and photographing residents and visitors from a rented house nearby, according to several officials briefed on the operation.
Observing from behind mirrored glass, C.I.A. officers used cameras with telephoto lenses and infrared imaging equipment to study the compound, and they used sensitive eavesdropping equipment to try to pick up voices from inside the house and to intercept cellphone calls. A satellite used radar to search for possible escape tunnels.
Still, the spying operation had its limits: American officials would see a tall man occasionally take walks through the compound's courtyard, but they were never able to confirm the man was Bin Laden.
The C.I.A. surveillance team took pains to avoid detection not only by the suspected Qaeda operatives they were watching but by Pakistani intelligence and the local police.
The documents taken at the Abbottabad compound, according to American officials, show that Bin Laden was in touch regularly with the terror network he created. With his whereabouts and activities a mystery in recent years, many intelligence analysts and terrorism experts had concluded that he had been relegated to an inspirational figure with little role in current and future Qaeda operations.
A rushed examination of the trove of materials from the compound in Pakistan prompted Obama administration officials on Thursday to issue a warning that Al Qaeda last year had considered attacks on American railroads.
The documents include a handwritten notebook from February 2010 that discusses tampering with tracks to derail a train on a bridge, possibly on Christmas, New Year's Day, the day of the State of the Union address or the 10th anniversary of the Sept. 11, 2001, attacks, officials said. But they said there was no evidence of a specific plot.
An Obama administration official said that documents about attacking railroads were among the first to be translated from Arabic and analyzed. The materials, along with others reviewed in the intelligence cache, have given intelligence officials a much richer picture of the Qaeda founder's leadership of the network as he tried to elude a global dragnet.
"He wasn't just a figurehead," said one American official, speaking on the condition of anonymity, who had been briefed on the documents. "He continued to plot and plan, to come up with ideas about targets and to communicate those ideas to other senior Qaeda leaders."
The aggressive effort across the intelligence community to translate and analyze the documents has as its top priority discovering any clues about terror attacks that might be in the works. Intelligence analysts also were scrubbing the files for any information that might lead to identifying the location of Al Qaeda's surviving leadership.
Since Sunday night, counterterrorism officials have been alert to the possibility of new attacks from Al Qaeda.
Department of Homeland Security officials have reviewed potential terrorist targets and deployed extra security at airports. And in response to the new evidence seized at the Bin Laden compound, the Transportation Security Administration issued a bulletin to rail companies.
But officials emphasized that the information was both dated and vague. "It looks very, very aspirational, and we have no evidence that it developed beyond the initial discussion," said Matt Chandler, a Homeland Security spokesman.
As the Bin Laden trail grew cold and he stopped broadcasting videos to the world in the last several years, his status as the world's most influential terrorist seemed to diminish. Still, in the decade since he fled Afghanistan in late 2001, he managed to release four to six audio messages each year, often making reference to current events, showing that his hide-out was not entirely cut off from the outside world.
"If he could get six audio messages out in a year, he could certainly get instructions to his followers," said Ben N. Venzke, who runs IntelCenter, a Virginia company that tracks terrorist groups' Internet communications.
The fact that Bin Laden was found not in Pakistan's rugged tribal areas but on the outskirts of an affluent town less than an hour's drive from the capital, Islamabad, has prompted a rethinking of the widespread notion that he had little control over the rest of Al Qaeda.
"Until now, the prevailing wisdom was that he was hiding in a remote, isolated mountain range and cut off from his followers," said Bruce Hoffman, an expert on Al Qaeda at Georgetown University. "Now we know that was all wrong and reconsider what his role really was."
Even with his death, American officials and terrorism experts have warned since Sunday night that that is not the end of Al Qaeda. Secretary of State Hillary Rodham Clinton, in Rome for talks about the war in Libya, told international donors on Thursday that the United States would continue aggressive operations against militants.