Officials said Abdul Mutallab, 23, tried to detonate an explosive device, apparently a mix of powder and liquid, as the flight, coming from Nigeria via Amsterdam, was approaching Detroit.
Peter King, the senior Republican on the House of Representatives Homeland Security Committee, told Fox News channel: "When it did go off, [Abdul Mutallab] himself was seriously injured. He has third-degree burns."
A senior homeland security official was quoted by the New York Times as saying that the device "was made from a mixture of powder and liquid" and was "more incendiary than explosive".
Too early to say
The official said Abdul Mutallab told authorities he had explosive powder taped to his leg and used a syringe filled with chemicals to mix with the powder in an attempt to cause an explosion.
A federal counterterrorism official was quoted on the Boston Globe
newspaper's website as saying that Abdul Mutallab was apparently in a government law-enforcement intelligence database, but it was not clear what extremist group or individuals he might be linked to.
"It’s too early to say what his association is," the counterterrorism official said.
"At this point, it seems like he was acting alone, but we don't know for sure."
Although Abdul Mutallab is said to have told officials that he was directed by al-Qaeda, the counterterrorism official expressed caution about that stance, saying "it may have been aspirational".
NBC television, citing counterterrorism officials, said Abdul Muttalab "claims to have been acting on his own."
King told CNN: "My understanding is ... that he does have al-Qaeda connections, certainly extremist terrorist connections, and his name popped up pretty quickly" in a search of intelligence data bases.
Homeland security said enhanced security measures had been put into effect after the failed attack.
"Passengers may notice additional screening measures put into place to ensure
the safety of the travelling public on domestic and international flights," it said in a statement.
President Barack Obama, who is currently on holiday in Hawaii, was "actively monitoring" the situation, a White House spokesman said.
"The president was notified of the incident this morning between 9am (07:00 GMT) and 9.30am Hawaii time by the president's military aide," Bill Burton said in a statement.
After Obama was informed of the incident he held a secure conference call with John Brennan, his homeland security and counterterrorism adviser, and Denis McDonough, the National Security Council chief of staff .
"[Obama] asked to arrange a subsequent secure call and... instructed that all appropriate measures be taken to increase security for air travel," the White House said.