The explosives packed into the black suede basketball boots of Richard Reid, who allegedly tried to blow up a US jet last Saturday, were reportedly bought from an arms dealer in Amsterdam found via the internet.
Mr Reid, the so-called "shoe bomber", told FBI investigators that he bought the plastic explosive – thought to be Semtex – for $1,500 (£1,100) after travelling to the Dutch city.
The allegations came as further details emerged of the improvised device found in the shoes of the 28-year-old Briton on board American Airlines flight 63 from Paris to Miami.
Traces of a substance known as PETN, a booster used in plastic explosives such as Semtex and a military explosive called C4, are believed to have been found in Mr Reid's shoes during tests. PETN, or pentaerythritaltetranitre, greatly increases the power of explosives, and is used in a number of fuses for devices containing Semtex and C4.
Agents said the shoe device was in effect a "home-made bomb", which might have failed to explode because its non-metal fuse was too damp to light. Mr Reid was overpowered after a flight attendant smelt sulphur from a lit match as he apparently tried to set the device off.
Mr Reid, 28, originally from Bromley, south London, who was converted to Islam, had spent much of the six months before his arrest travelling, visiting at least seven countries, including Israel, Egypt, Pakistan, Turkey, France, Belgium and the Netherlands.
Vincent van Steen, a spokesman for the BVD, the Dutch secret service, said it was "very probable" that Mr Reid had been in Amsterdam recently.
It is understood that he tracked down a seller of the explosive through a website and then travelled to the Dutch city after renewing his British passport in Brussels on 7 December.
Sir John Stevens, the Metropolitan Police Commissioner, has admitted that British intelligence agencies had not been aware he was a potential security risk. Sir John said information about him held by foreign intelligence officials was not passed on.
Mr Reid was questioned by Israeli officials when he took an El-Al flight to Tel Aviv in July.
Sir John told BBC Radio 4's Today programme that closer co-operation was needed between intelligence agencies to ensure information on terrorist suspects was freely available. "We have to make sure that our relationships with other law enforcement agencies around the world in terms of our war against terrorism are better," Sir John said. "We have got to know a lot more about some of the groups that are in this country who may well be involved in unlawful acts."
Mr Reid is a first cousin of the cricketer Danny Law, 26, who played for Essex and Sussex and is now a member of the Durham side. He said he had had "very little contact" with Mr Reid.Reuse content