Officials: 'Treasure trove' followed al Qaeda arrest
Capture of suspect in Pakistan led to terror alerts
Counterterror officials have an "intelligence report by the enemy."
Al Qaeda information gathering is chilling, officials say.
Tom Ridge raises the terror threat level for financial centers.
(CNN) -- The recent arrest in Pakistan of a computer expert with suspected ties to al Qaeda turned up evidence that the terror network has kept key U.S. financial buildings under surveillance, possibly for years, U.S. officials said Monday.
One U.S. intelligence official said the arrest yielded a "treasure trove" of information.
"Recent credible and specific intelligence reporting indicates terrorist operatives have done extensive research and reconnaissance activity," says an FBI bulletin sent Sunday to 18,000 federal, state and local law enforcement agencies.
A senior military official said a computer seized from the suspect in Pakistan contained hundreds of images, including photographs, drawings and layouts of potential U.S. targets.
Some of the photos were years old, while others had been taken as recently as the past few months, he said. Some images showed underground garages, leading to the conclusion that those areas had been under surveillance.
The Department of Homeland Security has said the New York Stock Exchange and the Citigroup headquarters in Manhattan; the Newark headquarters of Prudential Financial Inc.; and the Washington offices of the World Bank and IMF could be targets in a terrorist plot.
"The reporting does not specify the timing or mode of attack. Based on the nature of reconnaissance information, however, the most likely means of attack would be a vehicle borne improvised explosive device, to include limousines, large vans, trucks, and oil tankers which could be placed in underground parking areas or near highly populated entrance ways," the FBI bulletin says. (Full story)
Senior government sources said the stream of intelligence revealed more than the five financial targets that officials have publicly named. These sources described the additional targets as financial institutions.
A Homeland Security official acknowledged there were a number of what he called "minute mentions," without any details, of other buildings. The official would not elaborate further.
Scope of planning 'chilling'
The FBI has several investigations under way, stemming from the new intelligence, officials said.
One goal is to try to determine who carried out the surveillance and whether that person or people are still in the United States. Investigators are scanning employee and visitor records from the various sites.
In Washington, senior intelligence officials characterized al Qaeda's reconnaissance information as "chilling" in its scope and breadth.
Metropolitan police Chief Charles Ramsey and Capitol Hill police Chief Terrance Gainer said they expect the increased security around the buildings to remain in effect through at least the election November 2.
"I don't see anything on the horizon that would significantly change our posture prior to the election," Gainer said.
As part of the increased security, police around the U.S. Capitol have begun inspecting every car that drives by the Capitol and its office buildings.
Police will operate roughly 10 "vehicle screening checkpoints" around the perimeter of the Capitol complex, including heavily traveled Constitution and Independence Avenues from about 3rd Street on the west side and 2nd Street on the east side.
A U.S. official said the Pakistani computer expert, whom he identified as Muhammad Naeem Noor Khan, was a possible link to other al Qaeda operations, with information flowing through him by computer. (Full story)
The 25-year-old suspect was arrested July 13 in Pakistan.
Pakistani authorities said the man's identity could not be confirmed because he has used multiple aliases in the past.
CNN's Barbara Starr, Kelli Arena, Syed Mohsin Naqvi and Kevin Bohn contributed to this report.