Failed Xmas attack raises new security concerns

U.S. counterterrorism officials are scrambling to assess a potential new threat from an explosive mixture that evaded detection aboard a Detroit-bound airliner but failed to bring down the plane.

Multiple law enforcement officials said the suspected attacker _ identified as a Nigerian man named Umar Farouk Abdul Mutallab _ claimed to have acted on instructions from al-Qaida to detonate the explosive device over U.S. soil. The law enforcement officials spoke on condition of anonymity because they were not authorized to discuss the case.

The law enforcement officials cautioned that such claims could not be verified immediately, and said the man may have been …