ASHINGTON, Dec. 23 ?The Justice Department announced today that laboratory tests confirmed that explosives packed with wires had been hidden in the sneakers of a 28-year-old man who was violently subdued by passengers and flight attendants aboard an American Airlines jet over the Atlantic.

Investigators said they were not immediately able to establish any tie between the man and terrorist groups, including Osama bin Laden's Al Qaeda network, and that his motives remained a mystery.

The man, identified in court documents as Richard Colvin Reid, a British citizen who may be of Jamaican ancestry, was tackled and tied to his seat after he was seen lighting two matches and appearing to try to detonate the explosives during the flight from Paris to Miami.

Although investigators said the suspect had told the F.B.I. that he was a convert to Islam, they have turned up nothing to link him to Muslim extremists, like those blamed for the Sept. 11 terror attacks in the United States.

"Preliminary analysis by the F.B.I. laboratory in Washington has determined that there were two functional improvised explosives devices recovered from Reid's sneakers," the Justice Department said in a statement released in Boston, where the plane landed on Saturday afternoon after it was diverted from Miami.

The statement did not identify the explosive material, but Massachusetts State police officials said the preliminary tests suggested that it was C-4, a powerful military-grade plastic explosive that has been used by a variety of terrorist groups, including Al Qaeda.

Federal officials investigating Saturday's incident said it was unclear whether there was enough explosive material in the man's sneakers, or if it was of sufficient potency, to bring down the American Airlines Boeing 767-300, which was about a third of the way across the Atlantic Ocean, with 183 passengers and a crew of 14, when the incident occurred.

The suspect's identity remained in question. In London, Scotland Yard said in a statement that the man in custody in Boston was believed to be a British citizen.

But in Paris, where airport officials struggled to explain how a man carrying explosives had boarded a commercial jet, the French authorities were quoted in news reports as saying that the suspect was a Sri Lankan Muslim named Tariq Raja, traveling on a false British passport.

Congressional and law enforcement officials in Washington said that in an initial interrogation in Boston, the suspect insisted to F.B.I. agents that he was British ?with an English mother and a Jamaican father ?and that he was a relatively recent convert to Islam.

Other passengers on the flight said that the man, who had a ponytail and was more than six feet tall and appeared to weigh more than 200 pounds, spoke perfect English. After he was subdued and tied to his seat with the belts of other passengers, one asked him if he had tried to blow up the plane, and why. "You'll see," he is reported to have snarled.

The terrifying incident over the Atlantic, which ended only after passengers tackled the man as he tried to light a match and set the tongue of one of his sneakers on fire, drew expressions of alarm from members of Congress and from groups representing the interests of airline passengers.

Senator Richard C. Shelby of Alabama, the ranking Republican on the Intelligence Committee, said it was too early to say if the suspect was acting on his own or was part of an organized terrorist group like Al Qaeda, which has been blamed for the Sept. 11 terrorist attacks.

"I believe that the message here is ?as this unfolds ?that the terrorists are going to hit us again," Mr. Shelby said on CBS, shortly after receiving an F.B.I. briefing today on the case. "Is this part of a widespread deal, or is this guy acting alone? We don't know yet."

"But I think all of us have to be on alert," he continued. "We've known there would probably be reprisals by terrorists or terrorist groups because of what's happened in Afghanistan, our success there, and I think this is just one incident."

He said that whatever the outcome of the investigation, the incident showed that "although we've made a lot of headway since Sept. 11th as far as air safety, we've got a long way to go."

In Washington, the Federal Aviation Administration issued an order to airlines and airports tonight to guard against passengers who might board a plane with explosives hidden in their shoes. As a result, there was a common scene at major airports around the country tonight, as passengers traveling in the midst of one of the busiest holiday weekends of the year were asked to take off their shoes to be inspected.

On Dec. 11, the F.A.A. issued a warning to airports and airlines about the possibility that passengers might try to conceal weapons in their shoes. Officials said today that the Dec. 11 warning did not mention explosives and was not based on any intelligence reports or specific threats. It resulted instead, they explained, from an incident last year in which a man in the Philippines tried to hijack a plane with a gun smuggled aboard his shoe.

French authorities were investigating today why the man was able to pass through security at Charles de Gaulle Airport in Paris, where officials say they have taken extraordinary security precautions since Sept. 11, especially for planes bound for the United States.

Bush administration officials said today that the man arrested in Boston should have come under suspicion in Paris on Saturday for several reasons, including the fact that he was reportedly turned away from boarding the same American Airlines flight the day before.

Massachusetts Port Authority officials said they had been told that the man was detained on Friday at the Paris airport and questioned after raising suspicions because he did not check in luggage. On Saturday he was not stopped and was allowed to board the flight, which left Paris about 11:30 a.m. ?5:30 a.m. Eastern time.

But again on Saturday, he did not check any luggage. In Paris, the Air and Frontier Police, which is responsible for security at the airport, said its officers were supposed to be alerted by an airline's check-in counter whenever a passenger for an international flight arrives without luggage. But on Saturday, they said, that did not happen.

Since their harrowing flight, passengers from American Airlines Flight 63 have expressed concern about other security precautions at the Paris airport. At least two said in interviews that they had been upset to discover that the duty-free shops in the airport sold razors and several other items that could have been used as weapons.

Terrorists have apparently plotted to conceal explosive material in their shoes in the past.

Ramzi Ahmed Yousef, who was convicted of the 1993 bombing of the World Trade Center, was also convicted in a separate trial in 1996 of plotting to blow up a dozen jumbo jetliners in Asia to protest American support of Israel. Part of that plan involved hiding two nine-volt batteries in his shoe to power light-bulb filaments that would spark the explosion of liquid nitroglycerine explosives he planned to smuggle on board.

Another man convicted in the foiled jetliner plot, Abdul Hakim Murad, said in a January 1995 statement that a small amount of plastic explosive would have been hidden in his shoes. "Nobody can catch it because when you enter that, the X-ray, I mean the rays are a little bit up from your shoes," Mr. Murad said. "You can pass that."

The F.B.I. and the United States attorney's office in Boston said tonight that the suspect identified as Richard Reid had been charged with "interfering with the performance of the duties of flight crew members," a crime that carries a maximum prison sentence of 20 years, and that other criminal charges might be considered.