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Flight 253, with 289 people on board, sits on a tarmac in Detroit on Friday after arriving from Nigeria via Amsterdam. A passenger aboard the plane apparently tried to set off an explosive device. ((J.P. Karas/Associated Press))

A man who admits to being an al-Qaeda supporter tried to blow up a Northwest Airlines plane Friday as it was preparing to land in Detroit, but travellers who smelled smoke and heard what sounded like firecrackers rushed to subdue him, passengers and federal officials said.

Flight 253 — with 278 passengers and 11 crew members aboard — was about 20 minutes from the airport when passengers heard popping noises, witnesses said.

At least one person climbed over others and jumped on the man, identified as a Nigerian. Shortly afterward, the suspect was taken to the front of the plane with his pants cut off and his legs burned, a passenger said.

One U.S. intelligence official said the explosive device was a mix of powder and liquid. It failed when the passenger tried to detonate it.

"It sounded like a firecracker in a pillowcase," said Peter Smith, a traveller from the Netherlands. "First there was a pop, and then [there] was smoke." Smith said a passenger sitting opposite the man climbed over people, went across the aisle and tried to restrain the man.

Syed Jafri, another passenger, said he saw a glow and smelled smoke. Then, he said, "a young man behind me jumped on him."

Smith said the heroic passenger appeared to have been burned.

The White House said it believed it was an attempted act of terrorism and stricter security measures were quickly imposed on airline travel. It did not specify what those were.

Law enforcement officials identified the suspect in Friday's attempted attack as Umar Farouk Abdul Mutallab. One law enforcement official said the man claimed to have been instructed by al-Qaeda to detonate the plane over U.S. soil.

The man was being questioned Friday evening. An intelligence official said he was being held and treated in an Ann Arbor, Mich., hospital.

Flight 253 began in Nigeria and went through Amsterdam en route to Detroit. There was nothing out of the ordinary about the flight until it was on final approach to Detroit, said Federal Aviation Administration spokeswoman Elizabeth Isham Cory.

That is when the pilot declared an emergency, she said. The flight landed at 12:51 p.m. ET, she said.  Delta Air Lines Inc., which bought Northwest last year, said that "upon approach to Detroit, a passenger caused a disturbance." It said the passenger was subdued immediately and the crew asked that law enforcement officials meet the flight.

Melinda Dennis, who was seated in the front row of the plane, said the man involved was brought to the front row and seated near her.  She said he was taken off the plane handcuffed to a stretcher.

U.S. President Barack Obama was notified of the incident and discussed it with security officials, the White House said. It said he is monitoring the situation and receiving regular updates from his vacation spot in Hawaii.

Homeland Security Secretary Janet Napolitano was also been briefed and officials say she is closely monitoring the situation.

The department encouraged travellers to be observant and aware of their surroundings and report any suspicious behaviour to law enforcement officials.