Security services in Great Britain knew three years ago that the Detroit plane bomber had "multiple communications" with Islamic extremists in the U.K., according to officials.
Counterterrorism officials said Umar Farouk Abdulmutallab was "reaching out" to extremists whom MI5 had under surveillance while he was studying at University College London.
Officials said the 23-year-old Nigerian was "starting out on a journey" in Britain that culminated in his attempt to bring down Flight 253 as it prepared to land in Detroit on Christmas Day.
None of the information was passed to American officials.
British officials have passed a file to their U.S. counterparts on Abdulmutallab’s activities in Britain while he was a student from 2005 to 2008. It shows his repeated contacts with MI5 targets who were subject to phone taps, e-mail intercepts and other forms of surveillance.
Intelligence officials have defended their decision not to flag Abdulmutallab as a possible terrorist risk. They say he was one of many youths who mix with extremists, but are not themselves thought to be involved in plotting or supporting terrorism.
A senior British government official said the intelligence agency had conducted a quick assessment of Abdulmutallab while he was living in London and concluded he was not a threat to national security.