Officials cite three pieces of evidence to support the claim, reports Martin. First, the 500 pages of surveillance files stored in the computer of an al Qaeda operative captured last month in Pakistan have been transmitted to other operatives in the past year.
Second, the captured al Qaeda man, who goes by the name Abu Talha, has provided evidence of phone calls between al Qaeda operatives and someone in the U.S. within the past year.
Third, under questioning Talha has said based on what he knows, al Qaeda could still be planning an attack on U.S. financial institutions.
Besides pointing out safety concerns for the buildings in New York, Washington and Newark, N.J., the evidence indicates the presence of al Qaeda operatives inside the U.S.
Also Wednesday, the Bush administration learned from an imprisoned terror suspect, separately from the documents and two prisoners named this week, that al Qaeda was plotting to attack U.S. financial buildings, officials said Wednesday, rejecting criticism that the government's latest terror warning was overblown.
The White House described the latest information as "another new stream of intelligence" that supported its decision to issue warnings. It arrived days before the public alert, even as officials were reviewing reams of documents and photographs that showed surveillance of five such financial buildings in New York, New Jersey and Washington carried out years ago by al Qaeda.
"Old information isn't irrelevant information — particularly with this kind of enemy," Homeland Security Secretary Tom Ridge said Wednesday in Nashville, Tenn.
The information gained by the Bush administration corroborating al Qaeda's intentions to carry out attacks against U.S. financial buildings came from an imprisoned terror suspect other than two recently captured suspects in Pakistan, said a senior Justice Department official, speaking on condition of anonymity.
Information from those two suspects — a young militant familiar with computers and a man indicted in the U.S. Embassy bombings in Africa in 1998 — had provided the bulk of the intelligence that led to Sunday's warnings.
The corroborating information did not specify targets in the United States or say when an attack might be planned, the official said. But it so closely tracked the other intelligence that U.S. financial buildings had already been under surveillance by al Qaeda that it contributed to the decision to issue the public warnings.
"Coupled with general threat reporting, coupled with other pieces of information, then all of the sudden you say to yourself, 'This is a time when we have to talk to America about the threat.' And that's exactly what we did," Ridge said.
A U.S. counterterrorism official, also speaking on condition of anonymity, said the surveillance information last week was married with "very recent and current activity" from al Qaeda, indicating the group's interest in attacking this year. This information, which includes debriefings and other means of gathering information, is causing the administration serious cause for concern, the official said.
The FBI is monitoring al Qaeda operatives and others associated with Islamic terror groups inside the United States, although these people have not been directly linked to the threat against financial buildings, the Justice Department official said. These people include financiers for Ansar al-Islam, the official said.
White House spokesman Scott McClellan declined to describe in detail what he called "another new stream of intelligence," saying it might endanger continuing intelligence operations. He criticized as an "irresponsible suggestion" any criticism that the administration had issued a terror warning for political purposes.
"When you connect all these streams of intelligence, it paints an alarming picture," McClellan told reporters aboard Air Force One during a campaign flight to Iowa.
Ridge and other senior administration officials spent a second day Wednesday defending the warnings, which came on the heels of the Democratic National Convention and drew attention from the presidential campaign of nominee John Kerry.
"I categorically state that the none of the terror threats are politically motivated," Ridge said.
In New York, Treasury Secretary John Snow said suggestions that terror alerts were manipulated were "pure, unadulterated nonsense." Snow toured the floor of the New York Stock Exchange and praised traders for their resilience in the face of such warnings.