Investigators say they're closer to finding the man they believe masterminded the car bomb plots foiled Friday.
And it's now emerging that nightclub and pub owners throughout London were warned weeks ago of an impending bomb threat -- a warning that never made it to the general public.
The warning was sent out earlier this month based in part on intelligence that al Qaeda had targeted nightclubs and other soft targets before, and would likely do so again.
It's an al Qaeda trademark: If at first you don't succeed, try again.
Videos posted on al Qaeda Web sites show in detail how to rig propane and butane cylinders as bombs -- powerful bombs.
London nightclubs have been on the hit list before. And it was just last year that an al Qaeda operative by the name of Dhiren Barot was convicted by a British court in a plot to use limousines to carry such bombs to similar targets.
In his own manual, Barot described how the cylinders, "if carefully orchestrated can be as powerful as exploding TNT," and, "are easily available to the general public," designed for a "synchronized, concurrent [back-to-back] execution on the same day and time.
British officials tell ABC News a surveillance photo of the driver of the silver Mercedes bears a close resemblance to one of Barot's associates who was initially arrested three years ago but later released for lack of evidence.
Barot's men reportedly carried out surveillance of banks and corporate headquarters in London, Washington, D.C. and the New York area.
Friday in New York, police said they were stepping up security patrols on mass transit and at major landmarks.
"We've increased the deployment of critical response vehicles, focusing on tourist sites, Times Square, Herald Square, theater district," New York Police Commissioner Ray Kelly said.
All of this comes just three weeks after what was described as an al Qaeda graduation ceremony for suicide bombers at a training camp in Pakistan. A video obtained by ABC News shows commanders sending teams of 50 to 60 men to the United States, Canada, Germany and Great Britain.