"We do not, we do not want individuals or families to start sealing their doors or their windows," said Ridge.
Nor, said Ridge, did the government have any plans to go to Red Alert, meaning that an attack was imminent.
"We have not received any additional intelligence that would lead us to either raise or lower the threat level at this time," he said.
Across the intelligence and law enforcement communities today, analysts were trying to sort out a steady stream of clues suggesting that al Qaeda has issued attack orders for what could be a two pronged strike -- one aimed at U.S. forces in the Arabian theater -- and another, possibly simultaneous attack, at a target on the U.S. east coast, reports CBS News Correspondent Jim Stewart.
The analysts seem most focused on the activities of Khalid Sheik Muhammed who already has overseen attacks on U.S. embassies in Africa, the bombing of the USS Cole and had overall command of the 9-11 attacks.
Muhammed, arguably the second most powerful man in al Qaeda now behind Osama Bin Laden, has been "actively recruiting for al Qaeda" over the past year, analysts say, and is believed to have "personally signed off on the future attacks."
The FBI's role in assessing those threats got a vote of confidence today from President Bush who visited the bureau for a pep talk.
A week after increasing the nation's terrorist alert status from yellow to "high risk" orange, President Bush told the gathering "This agency now understands that we're at war."
The president also outlined more of his plan to combine parts of the bureau with the CIA under George Tenent and form a new analytical office; one of whose functions would be to share more information with local police, right down to cops in their squad cars.
"We're doing everything in our power to make sure the homeland is secure," the president said.
Meanwhile, a senior government official said Friday the administration now believes some of the information which led to upgrading the terrorist alert status was likely fabricated.
Authorities drew that conclusion based on polygraphs given to terrorist suspects interviewed by the government, said this official, speaking on condition of anonymity. The apparent fabrication was first reported by ABC News.
But that information was not the sole basis for the decision to raise the alert status, the official said, adding that the change of the status from code yellow to orange was based on multiple intelligence sources and not a single tip.
"No one factor has led to this state of alert," White House spokesman Ari Fleischer said, though he declined to confirm that some of the information was false.
The official also said federal authorities have identified between 20 and 40 people in the United States that trained in al Qaeda camps in Afghanistan. Of those, "less than a dozen" are believed to have had recent contact with al Qaeda operatives overseas, this official said, commenting on a report first broadcast by NBC.
Authorities also are keeping tabs on roughly 600 al Qaeda "sympathizers" in this country, said the official, who cautioned that there may be many more who are unknown to law enforcement authorities.
While the administration stressed that business goes on in the nation's capital, signs of preparation for possible terrorism are everywhere. Members of Congress are being told to have necessary supplies ready in the event of evacuation while the government warned key industries about potential attacks.
"Everyone in (the Capitol) has remained calm but cautious," said Rep. Bob Ney, R-Ohio, chairman of the House Administration Committee. "There is not a panic situation here."
Even so, lawmakers were told to gather up supplies, sensitive documents, medicine and a laminated list of key phone numbers in case they have to leave quickly. Congressional staffers this week received training in how to operate "escape hoods" that protect against chemical and biological substances.
The security measures are the latest to follow last week's increase in the terror threat level. The threat is now orange, or high, second from the top on a color-coded scale of five. Red, or severe, means an attack was imminent or under way.
Other visible anti-terror security steps around Washington included officers carrying rifles in the Capitol complex and the deployment of anti-aircraft missile batteries.
A new bulletin from the FBI and the National Infrastructure Protection Center was issued to companies involved in such industries as telecommunications, energy, and banking and finance, as well as operators of water systems and electric utilities, law enforcement agencies and emergency services.
Officials believe al Qaeda could target these entities with chemical, biological or radiological attacks. Such an attack, officials say, could prompt terror and mass casualties and disrupt the regional or national economy.
For people who might be faced with or respond to an attack, the bulletin recommends reading the Chemical, Biological and Radiological Incident handbook available on the CIA Internet site.
The FBI bulletin urges people who come in contact with a suspect substance to "cover their mouths with a cloth while leaving the area, avoid touching surfaces and wash their hands thoroughly."