WASHINGTON - Government forensic investigators examining how militants manufacture improvised explosives have found indications of a global bomb-making network, and have concluded that Islamic militant bomb builders have used the same designs for car bombs in Africa, the Middle East and Asia, government officials said last week.
"Linkages have been made in devices that have been used in different continents," said one forensic expert involved in the intelligence effort. "We know that we have the same bomb maker, or different bomb makers are using the same instructions."
The previously undisclosed intelligence operation has expanded on studies of past cases such as investigations of the thwarted shoe-bomb attack aboard a Paris to Miami flight in December 2001.
In a test, detonation of a similar bomb on a grounded aircraft blew a 2 foot by 2 foot hole in the fuselage - a potentially catastrophic event aboard a pressurized plane in flight.
In another example of the investigators' work, bomb analysts have collected fragments from hundreds of improvised devices detonated in attacks in Iraq, including large car and truck bombings and smaller assaults using explosives packed in empty artillery shells and even concrete blocks. That project has led to a better understanding of the devices and to efforts to provide commanders in Iraq with faster countermeasures to help protect U.S. troops.
But there are many questions still unanswered about who is behind various bombings, including some of the major suicide bombing attacks in Iraq.
Intelligence analysts have said they believe that al-Qaida has been weakened by the campaign against terrorism and lacks a central command, as well as financial and recruiting structures. But the bomb investigations suggest that the network may still be disseminating bomb-making skills to a generation of militants who have fanned out around the world.
Many bomb makers may have learned how to make improvised explosives in the 1990s at Osama bin Laden's training camps in Afghanistan, and the methods taught there may be showing up elsewhere.
Intelligence analysts did not say there was evidence of a single controlling entity behind the construction of the larger car and truck bombs often used in the most deadly attacks, although they suggested that there might not be many people with the technical skills to build larger bombs.
While there is still debate about who is behind the bombings in Iraq, and none of the larger and most deadly attacks by suicide bombers have been solved, intelligence analysts said they believed that followers of al-Qaida or ideologically sympathetic allies might be involved in some of the bombings.
Examining tiny bits of bomb housings, wirings, detonation cords, fuses, switches, the chemical composition of the explosives and the electronic signatures of remote switching devices often used to detonate bombs, experts at the center have begun to compile a data bank about bombs. In some cases, forensic scientists have been able to obtain evidence of who made the bomb through a fingerprint or DNA material left on an explosive part.
The study of the unexploded device built into the sole of the shoe worn by Richard Reid, a British citizen who was sentenced to life in prison, is a model for how the analysis center will operate. In that case, forensic examiners were aided by Federal Aviation Administration and Transportation Security Agency experts.
Reid acknowledged that he was a follower of al-Qaida. But subsequent forensic investigation showed that the design of his shoe bomb followed specific instructional details in training manuals found by U.S. forces at training camps in Afghanistan. The design closely followed the manuals. For example, the fuse was cut at precisely the angle the manual advised.
It remains unknown who built the shoe bomb, but investigators doubt it was Reid. Forensic analysts found a partial fingerprint on the bomb and single strand of human hair, but neither matched Reid's.