DETROIT, Michigan?It started with a pop and a burst of flame, then a brave passenger jumped over his seat to tackle a suspected terrorist as a packed airplane descended toward Detroit on Christmas Day.

The suspect, a Nigerian man with reported links to al-Qaida, was taken to the front of the plane with his pants cut off and his legs burned, said a passenger of Northwest Airlines Flight 253, with 278 passengers and 11 crew aboard, on a journey that originated in Nigeria and stopped in Amsterdam on its way to Detroit.

Law enforcement officials said the burns indicated the explosive was strapped to his legs. One US intelligence official said the explosive device was a mix of powder and liquid. It failed when the passenger tried to detonate it.

?There was a pop. And everybody got a little bit startled. And then we looked around and saw nothing,? said Syed Jafry, who was sitting three rows behind the Nigerian.

?After a few seconds or so, there was a little bit of light, a little bit of?kind of flameish light and there was fire. And people began to panic almost. And everybody was rushing toward that area and tried to get water, a blanket and fire extinguisher.?

People nearby tried to put the flame out, but it went a bit higher. There was smoke. Screams. Cries for water.

A young man three or four rows behind Jafry did not panic, however. He rushed down the aisle and helped a handful of fellow passengers pounce on the suspect and put out the flames.

?He took care of that suspect. He handled him pretty good,? Jafry told CNN on Friday after spending nearly five hours at the airport while he and his fellow passengers were interviewed by law enforcement.

It was all over relatively quickly and the Airbus 330 landed about 10 or 20 minutes later, he said.

Witnesses told Detroit news station WDIV that they saw the suspect?who was sitting on a center seat?emerge from the bathroom with a pillow held over his stomach and a syringe in hand.

He then injected the syringe into something held in his stomach area?possibly a powdery substance?and smoke and flames quickly followed.

?It sounded like a firecracker in a pillowcase,? said Peter Smith, a traveler from The Netherlands. He 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.

Richard Reid case

The incident was reminiscent of Richard Reid, who tried to destroy a trans-Atlantic flight in 2001 with explosives hidden in his shoes, but was subdued by other passengers. Reid is serving a life sentence.

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-Qaida to detonate the plane over US soil. All the officials spoke on condition of anonymity because the investigation was continuing.

Another law enforcement official said Mutallab?s name had surfaced earlier on at least one US intelligence database, but not to the extent that he was placed on a watch list or a no-fly list.

Mutallab was being questioned on Friday evening. An intelligence official said the Nigerian was being held and treated in a hospital.

A spokesperson for police at the Schiphol airport in Amsterdam declined comment about the case or about security procedures at the airport for Flight 253.

Schiphol Airport, one of Europe?s busiest with a heavy load of transit passengers from Africa and Asia to North America, strictly enforces European security regulations, including only allowing small amounts of liquid in hand luggage that must be placed inside clear plastic bags.

Tighter security measures

There was nothing out of the ordinary about the flight until it was on final approach to Detroit, said Federal Aviation Administration spokesperson Elizabeth Isham Cory. That was when the pilot declared an emergency, she said.

Smith said while he was leaving the plane, he looked at where the man had been sitting and saw a pillow that seemed to have been burned.

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 his legs appeared to be badly burned and his pants were cut off. She said he was taken off the plane handcuffed to a stretcher.

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

Passengers can expect to see heightened screening, more bomb-sniffing dog and officer units and behavioral-detection specialists at some airports, but there will also be unspecified less visible precautions as well, officials said.

Holiday threat not seen

The FBI and the Department of Homeland Security issued an intelligence note on Nov. 20 about the threat picture for the holiday season, which was obtained by The Associated Press. At the time, officials said they had no specific information about attack plans by al-Qaida or other terrorist groups.

In 2003, al-Qaida leader Osama bin Laden purportedly marked Nigeria for liberation in a recording posted on the Internet, calling on Muslims in the oil-rich country to rise up against one of the ?regimes who are slaves of America.? But links to al-Qaida remained rare, though security forces claimed to break up such a linked terror cell in November 2007.

Security at Nigeria?s two major international airports in the capital Abuja and in its megacity Lagos remain a point of concern. Uniformed federal police officers often focus their time on keeping hagglers and taxi drivers out.

Bags quickly pass through X-ray scanners and those watching incoming passengers do not typically conduct tests for explosive residue on passengers? carry-on baggage nor shoes.

At the gate, airline workers often check passengers again with handheld metal detectors before they board their flight. Reports from AFP and AP