Wednesday, 19 September 2001 : "Various news"

"Yes, we have heard something about Sept. 22, but nothing specific," one source close to the investigation said. "We have information that leads us to believe that there could be more attacks very soon. The same murky sources that indicated something might be coming in the weeks before the attacks have indicated something may be happening this weekend. It is our hope that we can stop it."

Another official familiar with the investigation said preventing further attacks has become their first priority.

In the wake of the attacks, Sen. Judd Gregg (R-N.H.) has proposed making it mandatory that software developers give government security agents the "keys" to encryption programs when they are created, a position strongly opposed by many in the technology community who worry it could be used to invade the privacy of law-abiding computer users.

Phil Zimmermann, the creator of a popular encryption technology, said he believes the answer to catching the terrorists lies in human footwork rather than more surveillance technologies: "It's not practical to frisk everyone on the planet to find the one person with a box cutter."

...now suburban Maryland has become a major focus of the investigation. Teams of agents are visiting and revisiting hotels, gyms, stores and apartment complexes along the Route 1 corridor.

At least six of the hijackers ... were seen in Laurel, Bowie, Greenbelt and Beltsville [MD]. ... [I]n 1999, Waleed M. Alshehri, who was aboard the same flight as Atta, lived for a short time in a Vienna [VA] boarding house and took computer classes with his father in Tysons Corner [VA].