[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/12/29/abdulmutallab.jpg caption="Umar Farouk AbdulMutallab is accused of trying to blow up an airliner as it landed in Detroit on Christmas."]
Romulus, Michigan (CNN) - Part of an explosive device that failed to take down a plane last week was sewn into the underwear of the Nigerian man accused of igniting it, a law enforcement official told CNN Monday.
Umar Farouk AbdulMutallab is being held for allegedly trying to blow up a flight carrying 300 passengers on Christmas Day.
Al Qaeda in the Arabian Peninsula claimed responsibility Monday for the attack, saying it was in retaliation for alleged U.S. strikes on Yemeni soil.
In a message written in Arabic, dated Saturday and published Monday on radical Islamist Web sites, the group hailed the "brother" who carried out the "heroic attack."
The group said it tested "new kind of explosives" in the attack and hailed the fact that the explosives "passed through security."
"There was a technical problem that resulted in a non-complete explosion," the message said.