A former British university student - Umar Farouk Abdulmutallab - was led from an aircraft after allegedly trying to blow up 278 passengers and 11 crew members as it prepared to land in the US city of Detroit.
The would-be bomber was foiled only because his explosive device failed to detonate properly as Northwest Airlines flight 253 from Amsterdam prepared to land at Detroit airport.
As a Dutch video director and producer was hailed as a hero for jumping on the suspect and subduing him, MI5, the security service, and Scotland Yard were investigating whether the Christmas Day bomb plot was hatched in Britain
They were also seeking to establish whether Abdulmutallab, 23, who is the son of a wealthy Nigerian banker, was radicalised during his three years as an engineering student at University College London, which he left in June 2008.
Members of the security services and counter-terrorism detectives – who are liaising with the FBI and other US crime-fighting agencies – want to discover whether Abdulmutallab was a member of a previously unknown al-Qaeda network operating within Britain.
Whitehall sources told The Sunday Telegraph that MI5 had started to examine files of all known al-Qaeda suspects and sympathisers within Britain to establish whether the plot had been missed by the security services.
Sources said they believed it was possible that Abdulmutallab may have been on the fringes of groups being monitored, but the full extent of any possible connections with al-Qaeda may not be known for some time. Abdulmutallab allegedly told investigators that he had spent part of the past year in Yemen, an established al-Qaeda breeding ground.
He is also alleged to have said that it was while he was there that he obtained explosives for the attempted terrorist attack.
A Whitehall source said: “MI5 is obviously looking at its files to see whether Abdulmutallab was known to them. They will want to know who his associates are and what role, if any, they played in this attack.”
Police yesterday sealed off the street where the suspect lived in central London. A spokesman for Scotland Yard said: “We are carrying out inquiries in conjunction with the US authorities. Searches are being conducted as part of our ongoing inquiries.”
Abdulmutallab is said to have attempted to ignite an explosive device strapped to his leg as the Airbus A330 was preparing its final descent to Detroit. According to US intelligence officials, the bomb was a mixture of powder and liquid.
Abdulmutallab was set alight and suffered serious burns before being overpowered. Two passengers were also injured. As Britain introduced tougher security measures for US-bound flights on Saturday, it emerged that the suspect’s father claimed to have alerted American and Nigerian authorities about his son’s “activities”, having become concerned by his behaviour.
Umaru Mutallab, 70, a prominent banker and former minister, was said to be travelling from his compound in the north of Nigeria, where Muslims form the majority of the population, to the capital, Abuja, to brief security officials.
It is understood that the suspect had been on an intelligence database of suspected extremists in the United States, but he was not on the “no-fly list”, meaning he was known to the authorities but not considered high risk.
Gordon Brown has pledged to take “whatever action was necessary” to protect air passengers.
The Prime Minister said he had been in contact with Sir Paul Stephenson, the Metropolitan Police Commissioner, because of the “serious potential threat”.
“The security of the public must always be our primary concern,” said Mr Brown. “We have been working closely with the US authorities investigating this incident.”
Tighter security and carry-on bag limits were introduced yesterday at British airports for US-bound passengers.
Britons travelling to the US were told that their hand-baggage allowance had been reduced to one item.
In addition, all passengers underwent a second personal and hand luggage search before boarding. The new guidelines were introduced at the request of the US government.
Some passengers flying from Britain to America were also told that they would not have in-flight entertainment.
One passenger, Scott Cullen, 32, said: “Apparently the mapping system which you can use to monitor the plane’s progress is the problem as the American government believes it could be used as a terrorist aid.”
Abdulmutallab had flown on a KLM flight from Lagos to Schiphol airport, Amsterdam, before boarding the flight to the US. The suspect had been granted a visa to travel to the US in June 2008 – valid until June 2010 – after claiming that he planned to attend a religious ceremony.
The Christmas Day incident was reminiscent of the bomb attack by Richard Reid, who tried to destroy a trans-Atlantic flight in 2001 with explosives hidden in his shoes, but was subdued by other passengers. Reid, the so-called shoe bomber, is serving a life sentence.
Peter T King, the senior Republican on America’s House Homeland Security Committee, said: “This was the real deal. This could have been devastating.”
President Barack Obama was notified of the incident and discussed it with security officials, the White House said. Last night Mr Obama was said to have been receiving regular updates while on holiday in Hawaii.
The suspect’s alleged link with Yemen could be significant.
It was reported on Thursday that Yemeni war planes were believed to have killed two al-Qaeda leaders and a Muslim extremist religious leader connected with the US Army officer accused of killing Army personnel in Fort Hood, Texas, last month.
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