Tower Terror

A murderous explosion in the heart of New York City raises the specter of terrorism in America and sets off a feverish hunt for the bomber

By Richard Lacayo Monday, Mar. 08, 1993

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    Experts will also try to determine the velocity of the shock waves emanating from the blast. "Different compounds explode at different speeds," says Brian Jenkins, senior managing director for Kroll Associates, an international investigating firm. "You can tell by examining the metal that was torn apart. Was it a big explosion that moved a lot of things, or was it a high-velocity explosion that rent metal?" Sophisticated plastic explosives tend to shred metal and pulverize concrete, while common substances like dynamite tend to knock walls over and push vehicles around. Once investigators identify the substance, they will try to determine whether it was a homemade explosive, one made from commercially available material or a product of limited availability, like a military-grade explosive. If the material is common, the trail may be colder than if it is a closely monitored substance.

    Initial speculation in this case centers upon plastic explosives like Semtex, the lethal weapon of choice for many terrorists because it is safe to - handle and undetectable by sniffer dogs or X-ray inspection. A small amount hidden in a portable radio blew Pan Am Flight 103 out of the sky in 1988. Semtex was produced in quantity under the communist government of Czechoslovakia; while the postcommunist Czech Republic has discontinued production, large quantities remain in the hands of terrorist gangs that obtained them illicitly. Three years ago, Czechoslovak President Vaclav Havel estimated that "world terrorism has supplies of Semtex to last 150 years."

    Until last week, federal agents were confident that terrorist groups contemplating action on American soil would have considerable difficulty smuggling in enough high explosives to manufacture a sizable car bomb. Could they have obtained them in the U.S.? Although high explosives are widely used in the construction industry, they are monitored. The FBI maintains close contacts with manufacturers and dealers, while sales are tightly regulated by the Bureau of Alcohol, Tobacco and Firearms. Though the Pentagon possesses its own plastic explosive, a Semtex relative called C-4, a would-be terrorist would have to steal it from a military facility -- a theft that would probably be detected. Other explosives might be simpler to accumulate, however, like ammonium nitrate, an ordinary component of fertilizer that has been a favorite of the Irish Republican Army.

    Experts speculate that the bomb may have consisted of several hundred pounds of high explosives. The bomber may have known that because the device would be detonated in the reinforced enclosure of a garage, it would deliver more bang for the buck. An enclosed area can double the "shock wave" value of an explosion. "When you have a contained explosion, the blast doesn't vent," says Phil Hough, president of International Explosives Disposal (USA). "Effectively the building becomes part of the bomb." Says Phillips: "The garage was the perfect location because of both the damage to the upper floors ((with smoke)) and structural damage the bomb would cause at the base."

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