By JIM IRWIN


ROMULUS, Mich. (AP) - An attempted terrorist attack on a Christmas Day flight began with a pop and a puff of smoke - sending passengers scrambling to subdue a Nigerian man who claimed to be acting on orders from al-Qaida to blow up the airliner, officials and travelers said.

The commotion began as Northwest Airlines Flight 253, carrying 278 passengers and 11 crew members from Amsterdam, prepared to land in Detroit just before noon Friday. Travelers said they smelled smoke, saw a glow, and heard what sounded like firecrackers. At least one person climbed over others and jumped on the man, who officials say was trying to ignite an explosive device.

"It sounded like a firecracker in a pillowcase," said Peter Smith, a passenger from the Netherlands. "First there was a pop, and then (there) was smoke."

Smith said one passenger, sitting opposite the man, climbed over passengers, went across the aisle and tried to restrain the man. The heroic passenger appeared to have been burned.

Afterward, the suspect was taken to a front-row seat with his pants cut off and his legs burned. Multiple law enforcement officials also said the man appeared badly burned on his legs, indicating the explosive was strapped there. The components were apparently mixed in-flight and included a powdery substance, multiple law enforcement and counterterrorism officials said.

The White House said it believed it was an attempted act of terrorism and stricter security measures were quickly imposed on airline travel. Dutch anti-terrorism authorities said the U.S. has asked all airlines to take extra precautions on flights worldwide that are bound for the United States.

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.

Multiple law enforcement officials identified the suspect in Friday's attempted attack as Umar Farouk Abdul Mutallab. He was described as Nigerian.

One law enforcement official said the man claimed to have been instructed by al-Qaida to detonate the plane over U.S. soil, but other law enforcement officials cautioned that such claims could not be verified immediately, and said the man may have been acting independently - inspired but not specifically trained or ordered by terror groups.

All the officials spoke on condition of anonymity because the investigation was continuing.

Intelligence and anti-terrorism officials in Yemen said they were investigating claims by the suspect that he picked up the explosive device and instructions on how to use it in that country. The officials spoke on condition of anonymity because they are not authorized to speak to the media.

The man was being questioned Friday evening. An intelligence official said he was being held and treated in an Ann Arbor, Mich., hospital. The hospital said one passenger from the flight was taken to the University of Michigan Medical Center in Ann Arbor, but referred all inquiries to the FBI.

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.

One law enforcement official, also speaking on condition of anonymity, said Mutallab's name had surfaced earlier on at least one U.S. intelligence database, but he was not on a watch list or a no-fly list.

The suspect boarded in Nigeria and went through Amsterdam en route to Detroit, Rep. Peter King, the ranking GOP member of the House Homeland Security Committee, told CNN. A spokeswoman for police at the Schiphol airport in Amsterdam declined comment about the case or about security procedures at the airport for Flight 253.

Dutch airline KLM says the connection in Amsterdam from Lagos, Nigeria, to Detroit involves a change in carrier and a change in aircraft.

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.

A spokesman for the Federal Airports Authority of Nigeria, Akin Olukunle, said all passengers and their luggage are screened before boarding international flights. He also said the airport in Lagos cleared a U.S. Transportation Security Administration audit in November.

"We had a pass mark," Olukunle said. "We actually are up to standards in all senses."

Nigeria's information minister, Dora Akunyili, condemned the attempted bombing. She said the government has opened its own investigation into the suspect and will work with U.S. authorities.

"We state very clearly that as a nation we abhor all forms of violence," Akunyili said in a statement issued Saturday.

London's Metropolitan Police also was working with U.S. officials, a spokeswoman said, and searches were being conducted in that city. The spokeswoman would not provide additional details, including what connection the suspect had to London or what was being searched. She spoke on condition of anonymity in line with department policy.

Delta Air Lines Inc., which acquired Northwest last year, said a passenger caused a disturbance, was subdued, and the crew requested that law enforcement officials meet the flight.

Passenger Syed Jafri, a U.S. citizen who had flown from the United Arab Emirates, said the incident occurred during the plane's descent. Jafri said he was seated three rows behind the passenger and said he saw a glow, and noticed a smoke smell. Then, he said, "a young man behind me jumped on him."

"Next thing you know, there was a lot of panic," he said.

Federal officials said there would be heightened security for both domestic and international flights at airports across the country, but the intensified levels would likely be "layered," differing from location to location depending on alerts, security concerns and other factors.

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.

The FBI and the Homeland Security Department 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.

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