The blackened husks of pagers and handheld radios that exploded in a colossal attack on Hezbollah this week have become fragmentary clues to how Israel orchestrated what current and former Israeli and Western security officials said was part of an elaborate, decade-long effort to penetrate the militant group.

       Markings on the mangled electronic components have left a trail leading back through a manufacturer in Taiwan to a Hungarian shell company suspected of being set up or exploited by Israeli intelligence to disguise its alleged role in delivering the lethally rigged devices to Hezbollah. Security officials in another European capital have probed whether a second shell company there was the real seller behind the pagers deal.