Federal Bureau of Investigation analysis has identified the explosive pentaerythritol tetranitrate (PETN) as the substance alleged to have been used in the attack on a Delta Air Lines Airbus A330 on 25 December.
The FBI has formally charged a Nigerian national, Umar Farouk Abdulmutallab, with wilfully placing a destructive device on board the twin-jet, and attempting to destroy the aircraft, as it approached Detroit as flight 253 from Amsterdam Schiphol.
Affidavit documents filed by the FBI with the US District Court state that, while analysis is continuing, an item Abdulmutallab carried on board, attached to his body, "appears to have been an explosive device", specifically "an explosive bomb".
The FBI says that PETN was among the components of the device. PETN is a chemical which normally appears in the form of white, or colourless, crystals or powder. It can combust violently if exposed to heat or explode if subjected to shock.
Witnesses on board the aircraft, says the affidavit, state that Abdulmutallab was in the aircraft's bathroom for around 20min just before the incident. On returning to his seat, reportedly the left-hand window position 19A, he covered himself with a blanket complaining of a stomach upset.
"Passengers then heard popping noises similar to firecrackers, smelled an odour, and some observed Abdulmutallab's pants leg and the wall of the airplane on fire," says the document.
"Passengers and crew then subdued Abdulmutallab and used blankets and fire extinguishers to put out the flames."
One of the flight attendants stated that she asked the individual what he had in his pocket, and he replied: "Explosive device."
Another passenger witnessed an apparently partially-melted syringe, which was smoking. The FBI recovered the remnants of a syringe from Abdulmutallab's seat. The affidavit says that the syringe is "believed to have been part of the device", but does not indicate the nature of its contents.