At the New York Stock Exchange, Mayor Michael R. Bloomberg rang the opening bell. Exchange chief executive John A. Thain and Sen. Charles E. Schumer (D-N.Y.) greeted arriving workers. "I wouldn't be surprised if attendance weren't higher today," Schumer said. "We are winning the war of nerves."
Much of the information about the targeted buildings is contained on a laptop computer and computer disks recovered during recent raids in Pakistan. A senior intelligence official said the cache also includes about 500 photographs, diagrams and drawings, some of them digital.
Metro Transit Police officers gather outside the Farragut West station in downtown Washington as part of the stepped-up security prompted by the new alert.
(Robert A. Reeder -- The Washington Post)
Live, 1 p.m. ET: The Post's Dan Eggen will be online to discuss the latest terror alert warning.
Two senior intelligence officials who briefed reporters on Sunday said the material showed al Qaeda operatives had cased the buildings both before and after the Sept. 11 attacks.
"I think the indications are that this has been a very longstanding effort on the part of al Qaeda," one official said Sunday, "that it dates from before 9/11, it continued after 9/11 and based on what it is that we are concerned about, we know about in terms of al Qaeda's plans and intentions that it probably continues even today."
Speaking about the five buildings, one official said, "I believe that since 9/11 they have been able to acquire additional information on these targets here in the United States, yes, I do."
Numerous officials said yesterday, however, that most of the information was compiled prior to the Sept. 11 attacks and that there are serious doubts about the age of other, undated files. One senior counterterrorism official said many of the documents include dates prior to Sept. 11, 2001, but there are no dates after that.
"Most of the information is very dated but you clearly have targets with enough specificity, and that pushed it over the edge," the counterterrorism official said. "You've got the Republican convention coming up, the Olympics, the elections. . . . I think there was a feeling that we should err on the side of caution even if it's not clear that anything is new."
One federal law enforcement source said his understanding from reviewing the reports was that the material predated Sept. 11 and included photos that can be obtained from brochures and some actual snapshots. There also were some interior diagrams that appear to be publicly available.
Other officials also stressed that, however long ago al Qaeda operatives compiled the surveillance details, the information was new to U.S. intelligence agencies and was almost unprecedented in the depth of its details. "All this stuff was fresh to us," one official said.
At the CIA's daily 5 p.m. counterterrorism meeting Thursday, the first information about the detailed al Qaeda surveillance of the five financial buildings was discussed among senior CIA, FBI and military officials. They decided to launch a number of worldwide operations, including the deployment of increased law enforcement around the five buildings.
A senior intelligence official said translations of the computer documents and other intelligence started arriving on Friday. "We worked on it late, and through that night," he said. "We had very specific, credible information, and when we laid it in on the threat environment we're in," officials decided they had to announce it.
"It's not known whether the plot was active and ongoing," the official added. "It could have been planned for tomorrow, or it could have been scrapped. Maybe there were other iterations of it. In this environment, this was seen as pertinent information to get out to the public. There was discussion over the weekend, should we wait until Monday?"
Initially, top administration officials had decided to wait until yesterday to announce the alert, but more intelligence information was coming in -- both new translations of the documents, and analysis of other sources' statements -- that deepened their concern about the information, and persuaded them to move ahead swiftly. "There was a serious sense of urgency to get it out," the senior intelligence official said.
On Saturday, officials from the CIA, the FBI, the Homeland Security and Justice departments, the White House, and other agencies agreed with Ridge to recommend that the financial sectors in New York, Washington and North Jersey be placed on orange, or "high," alert. Ridge made the recommendation to Bush on Sunday morning, and Bush signed off on it at 10 a.m.
In a signal of how seriously the administration took the information, officials briefed senior media executives, including network anchors, before a Sunday news conference and briefing for reporters.
In New York yesterday, traffic backed up at tunnels and bridges into the city, Hercules and Atlas police teams toting rifles and machine guns checked vehicles, police helicopters crisscrossed the skies, and employees throughout the financial district stood in long security queues, showing their corporate identifications and bags to guards.
Around the NYSE in Lower Manhattan, rows of concrete and metal barricades were in place and side streets were blocked off.
In Newark, officials set up concrete barriers and police teams around the 24-story Prudential building, where about 1,000 employees work. "I'm a little nervous," analyst Tracy Swistak, 27, told the Associated Press. "But I'm confident Prudential's doing everything they can to ensure our safety."
Staff writers John Mintz, Allan Lengel and Spencer S. Hsu in Washington and Michael Powell, Michelle Garcia and Ben White in New York contributed to this report.