British intelligence passed on to U.S. authorities information about a Nigerian accused of trying to blow up a Detroit-bound airliner but he was not singled out as a particular risk, Prime Minister Gordon Brown's office said Monday.

Umar Farouk Abdulmutallab's name was included in a dossier of people who made contact with known extremists in the United Kingdom but officials believe he was radicalized after he left the country in 2008, according to Brown's spokesman, Simon Lewis.

The disclosure came a day after British security officials said they were aware that Abdulmutallab was in contact with known radicals shortly after he came to the U.K. in 2005 but did not consider him a sufficient threat to single him out and alert U.S. authorities.

Investigators say Abdulmutallab, a 23-year-old Nigerian who studied in engineering in London and later went to Yemen, sneaked an explosive device aboard his Northwest Airlines flight from Amsterdam to Detroit on Christmas Day but was not able to ignite it as planned.

A U.S. counterterrorism official said Monday the British government did not provide material on Abdulmutallab that could be termed a "smoking gun" _ meaning, information that would have alerted authorities to the bomb plot. The official declined to be named because he was not authorized to comment on the matter publicly.

President Barack Obama has said there was a systemic failure to prevent the attack and ordered a thorough review of security shortcomings. The president has summoned Homeland Security officials to meet with him in the White House on Tuesday.

"Clearly there was security information about this individual's activities, and that was information that was shared with the U.S. authorities," Lewis said. "That is the key point."

Downing Street would not immediately give any other specific details, including when the information was shared with U.S. authorities.

Although certain information was exchanged, Abdulmutallab wasn't considered violent or a threat to the United States so he was not flagged as a high-risk suspect to U.S. authorities, a British government official told The Associated Press on Monday. He spoke on condition of anonymity because of the sensitivity of his work and declined to elaborate on what information was shared.

"The U.S. had everything they required in terms of threat risks," the British official said.

British intelligence and counterterrorism officers routinely monitor people in the country with known links to extremists and or suspected links to terror financing. Many are not considered violent or high-risk priorities.