Officials: Arrest in Pakistan led to orange alert
Cities take additional defensive steps
Key institutions opened for business despite terror alert.
Counterterror officials have an "intelligence report by the enemy."
Al Qaeda information gathering is chilling, officials say.
WASHINGTON (CNN) -- Information seized from a suspected al Qaeda computer expert was largely responsible for the increased threat level for three East Coast financial districts, U.S. and Pakistani officials said Monday.
A U.S. intelligence official said the previously unannounced arrest of a 25-year-old computer expert July 13 in Pakistan yielded evidence that detailed potential attacks against New York; Newark, New Jersey; and Washington.
The U.S. official identified the man as Muhammad Naeem Moor Khan. But Pakistani authorities said the man's identity could not be confirmed because he has used multiple aliases in the past.
Khan was described as a possible "node" in al Qaeda operations, with information flowing through him, possibly by computer.
Ahmed Khalfan Ghailani -- a Tanzanian arrested last week in connection with al Qaeda's bombings of U.S. embassies in East Africa in 1998 -- also provided "very important" information, Pakistani Information Minister Sheikh Rashid Ahmad said Monday.
Also, a senior Pakistani intelligence official said seven more suspected al Qaeda members have been taken into custody since Ghailani's arrest -- including one who was trying to leave the country Monday morning.
Homeland Security Secretary Tom Ridge urged Americans on Monday to go about their business as usual, even though he said terrorists want to "undermine the economy of the United States."
Ridge said the intelligence suggested terrorists may be targeting the New York Stock Exchange and Citigroup headquarters in New York, insurance giant Prudential Financial's headquarters in Newark, and the International Monetary Fund and World Bank buildings in Washington. But he said nothing indicated the threat was imminent.
Ridge raised the color-coded alert level for terror threats in those areas from yellow, or elevated, to orange, or high.
"There was no mention of when an attack could occur, but we don't have the luxury of guessing," he said.
However, he said raising the threat level in specific areas will make the buildings safer and people in them more aware.
This is the first time the terror threat system has been used to raise the threat level in targeted areas, rather than nationwide.
A New York law enforcement source said reconnaissance information was so specific that it appears potential attackers may have conducted surveillance inside the buildings, perhaps over several years. (Full story)
Impact on cities
In New York, police stopped trucks and vans at toll booths.
Authorities banned commercial traffic from using the Holland Tunnel to travel from New Jersey into Lower Manhattan, and rerouted it to the Lincoln Tunnel and George Washington Bridge, which cross the Hudson River farther north of the financial district.
Officers with rifles and body armor patrolled the financial district.
New York Mayor Michael Bloomberg said he took the subway to work, and that the increased security "should give everybody comfort."
"New York City is not going to be cowed by the terrorists," Bloomberg said. "Make no mistake about that. We're not going to spare any expense in protecting us, but also, the people of New York City know that giving in to terrorism is exactly the wrong thing to do."
Metropolitan Police Chief Charles Ramsey said the Washington offices of the World Bank and IMF "were specifically mentioned."
"This is information that was uncovered. We'd be remiss if we didn't act on it like we did," he said. "This could have just been a plan that was a plan B or plan C and was never going to be implemented. We have no way of knowing."
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 November election.
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 about 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.
New Jersey Gov. Jim McGreevey said his state was "very well-prepared" and that the orange alert was being "implemented on an almost seamless basis."
"We're providing for strong employee identification," McGreevey said. "We've also instituted road barriers, very much as you would upon an entrance in terms of a military installation to provide police to be able to conduct surveillance.
"We have canine and bomb units out," he added. "Our state police are on ferries and trains, and we automatically implement every time we go to level orange certain safety protocols that are adopted by the financial-services industry."
CNN's Mike Brooks, Ed Henry, Suzanne Malveaux, Jamie McShane and Jeanne Meserve contributed to this report.