The federal government raised the terrorism alert level to "orange" for the financial services sectors in New York City, Washington and Newark, N.J., citing the discovery of detailed intelligence showing that al Qaeda operatives have been plotting for years to blow up specific buildings with car or truck bombs.

Homeland Security Secretary Tom Ridge said Sunday that the newly acquired information pointed to five potential targets: the International Monetary Fund and World Bank headquarters in Washington; the New York Stock Exchange and Citigroup Center in New York; and the Prudential Financial building in Newark, N.J.

But later it was reported that most of the al Qaeda surveillance was conducted before the Sept. 11, 2001, attacks on Washington and New York and that authorities are not sure whether the casing of the buildings continued, although one piece of intelligence on one of the buildings appeared to have been updated on a computer file as recently as last January.

Ridge said Tuesday that the fact that the al Qaeda computer files, which were seized in raids in Pakistan late last month, were updated this year led to the alert. "When you see this kind of detailed planning, you have to take preemptive action," he said.

Moreover, intelligence officials, speaking confidentially, said they relied on "multiple streams of intelligence" that they could not reveal -- including al Qaeda members in custody and captured documents -- that buttress their assertion that al Qaeda is actively plotting attacks on financial sites.

Meanwhile, Great Britain, acting in part on intelligence from Pakistan, arrested an al Qaeda member planning attacks on this country.

Security, including traffic checkpoints and street closings, has been increased near the U.S. Capitol, the IMF and World Bank headquarters, the Federal Reserve Board and the U.S. Treasury.

-- Dan Eggen, John Mintz

and Dana Priest

A New York City police emergency unit guards Citigroup headquarters Tuesday.