The presence of Pentrite in the wreckage, especially in the remains of the forward hold, does not necessarily mean it was destroyed by a bomb.

While it looks like nylon cord, the core is a compressed powdered explosive, usually PETN (pentrite), and it is initiated by the use of a blasting cap.

They are now certain an explosion was caused by Pentrite, a plastic explosive which requires much less skill to handle than Semtex and has been used by a far wider range of terrorist groups.

Officials said Abdulmutallab apparently assembled the explosive device, including 80 grams of Pentrite, or PETN, in the aircraft toilet, then planned to detonate it with a syringe of chemicals.

On Oct. 3, 1980, a bomb containing the powerful explosive pentrite hidden in the saddlebags of a parked motorcycle exploded outside the synagogue as hundreds of worshippers were gathered inside for a Sabbath service.

The French antiterrorism official would not identify the kind of explosive found other than to say that it contained pentrite, which is made from pentaerythritol, a compound used in the manufacture of explosives as well as insecticides.

But there have been no credible claims of responsibility, and the use of Pentrite suggests to secret service investigators that it may not have been aimed at French national interests but at someone on the aircraft.

Detonating cord (also called detonation cord, detacord, det. cord, detcord, primer cord or sun cord) is a thin, flexible plastic tube usually filled with pentaerythritol tetranitrate (PETN, pentrite).

Two of the caches were located Friday morning, with a third containing 25 kg (55 lb) of ammonium nitrate and 12 kg of pentrite, both explosive substances, discovered in the afternoon, a spokeswoman from the prosecutor's office said.

Bourles added some 30 detonators had also been unearthed along with an explosive device packed with some 500 grams (1.1 pounds) of pentrite, a powerful explosive, and other bomb-making equipment, including 200 kilograms of aluminium powder and 150 of ammonium nitrate.

Police on Tuesday found 850 kilogrammes (1,874 pounds) of ammonium nitrate fertilizer, 13.5 kilogrammes of the explosive pentrite and detonators in their pre-dawn raid at an isolated farm in Legorreta in the biggest explosives cache to be confiscated by police in Spain since 1999.