Taken from USA Today
Improvised explosives like the ones used in two bombs discovered in U.S.-bound cargo shipments are the weapon of choice for terrorists and will continue to be a threat because they are so difficult to detect, say security and terrorism experts. Despite a nearly decade-long effort to better screen for explosives, they continue to be used in attacks launched everywhere from Afghan and Iraqi war zones to hidden al-Qaeda strongholds. The PETN found hidden in toner cartridges is a military-grade explosive that has been used repeatedly by terrorists. Though officials have not described the bombs in detail, it appeared they each could have held 2 to 3 pounds of PETN, said Neal Langerman, an explosives expert who is an officer with the American Chemical Society. "It would have been enough to do significant damage wherever it detonated," Langerman said. If the bombs had exploded, they would have likely caused significant damage to the cargo jets that carried them, and killed or injured anyone nearby. To an enemy who cannot match our military might or easily penetrate our borders, a small, hidden bomb that can be assembled with easily obtained materials such as cellphones is an attractive weapon. "Explosives pack a lot of energy in a very small package," Langerman says. "That's what it's all about."