The assembly was unusual because it did not rely on a standard miniaturised detonator, typically a metallic cylinder, the source and two bomb experts said. All three spoke on conditions of anonymity.

Without any metal components, the material used to trigger detonation had an edge: like the plastic explosives, it was not detected by X-ray.

Upon receiving the pagers in February, Hezbollah looked for the presence of explosives, two people familiar with the matter said, putting them through airport security scanners to see if they triggered alarms. Nothing suspicious was reported.

So apparently all these airport X-rays I’ve been doing since 9/11 don’t stop explosives after all?