Investigators are saying it could be days or even weeks before they know if last week's al Qaeda bomb plot using cargo shipments from Yemen has been fully contained.
Security teams are tracking down other shipments from Yemen that could potentially contain explosives.
German officials revealed this week that the bombs found on planes in England and Dubai Oct. 29 had more than a pound of the deadly explosive PETN. If the bombs had exploded, one German security agent said the effect would have been significant.
That has led Germany to ban not only all cargo flights from Yemen, but all passenger planes.
Meanwhile, a frantic search continues for all packages shipped from Yemen to the U.S. during the last two weeks, in case other bombs have slipped through already and the world has to face a new wrinkle in al Qaeda's war of terror.
"I think they want to inflict damage, death and destruction on the United States. And we're going to have to now look for a whole wide range of tactics," Former Secretary of Homeland Security Michael Chertoff said.
Officials now expect the sophisticated bombs were supposed to be triggered on U.S. bound flights, maybe just as they were coming in over large American cities.
"The device would be safe until the circuit board receives a signal which would cause a switch that is normally open to close," Kevin Barry, a former NYPD bomb squad supervisor, said.
Saudi officials became aware of the mail bomb plot from a leading al Qaeda member who gave himself up to the Saudis last month. They suspect an al Qaeda bomb-maker, Ibrahim al-Asiri, put the devices together, hiding them inside desktop printers. Al-Asiri is the same man who made the bomb for the infamous Christmas day "underwear bomber."
"They are trying to again make different types of adaptations based on what we have put in place. So the underwear bomber, as well as these packages, are showing sort of new techniques on their part," White House Homeland Security Advisor John Brennan said.
The Oct. 29 bombs were addressed to synagogues in Chicago, prompting a solidarity rally with Jesse Jackson and various Jewish leaders.
"When a house of worship is under threat in this country, all houses of worship are threatened," Rabbi Michael Siegel, with Anshe Emet Synagogue, said.