Bush administration officials said the FBI believed an explosion occurred aboard the jet, and witnesses reported hearing one and seeing an engine fall off. But investigators suggested the noise was caused by a catastrophic mechanical failure, and a senior administration official, speaking on condition of anonymity, said: "It's looking like it's not a terrorist attack."

Still, the city - on edge after the Sept. 11 attack in which hijacked airliners brought down the World Trade Center - was put on high alert in the minutes and hours after the crash.

Fighter jets flew over the scene in the Rockaway Beach section of Queens. All metropolitan-area airports - Kennedy, LaGuardia and Newark, N.J. - were closed, and international flights were diverted to other cities. Bridges and tunnels were closed to incoming traffic. The United Nations was partially locked down, and the Empire State Building was evacuated.

Flight 587, an Airbus A300 with 246 passengers and nine crew members aboard, went down at 9:17 am in clear, sunny weather in the waterfront neighborhood 15 miles from Manhattan. The densely populated section is home to many firefighters who were among the dead and the rescuers at the Trade Center.

"I heard the explosion and I looked out the window and saw the flames and the smoke," said Milena Owens, who lives two blocks from the crash site and was putting Thanksgiving decorations on her window. "And I just thought, `Oh no, not again.'"

Witnesses reported hearing an explosion and seeing an engine and other debris falling off the flaming twin-engine jet as it came down. An engine was found intact in a parking lot at a Texaco station, missing the gas tanks by no more than 6 feet. Part of a wing appeared to be in Jamaica Bay, just offshore, Mayor Rudolph Giuliani said.

A plume of thick, black smoke could be seen miles away; flames billowed high above the treetops.

"I don't believe there are any suvivors at this point," Giuliani said.

Roberto Valentin, a Dominican ambassador at large, said he believed 90 percent of the passengers were Dominican.

At least 15 people were reported injured on the ground.

Four houses were destroyed, four were seriously damaged, and as many as a dozen others sustained lesser damage, the mayor said.

Jennifer Rivara said she was looking out a window from her home about five blocks from the scene. "I saw pieces falling out of the sky," she said. "And then I looked over to my left and I saw this huge fireball, and the next thing I know, I hear this big rumbling sound. I ran to the door and all I saw was big black smoke."

In Washington, White House spokesman Ari Fleischer said there were no "unusual communications" from the cockpit. And a senior administration official said that no threats against airplanes had been received.

The National Transportation Safety Board was designated the lead agency in the investigation, signaling that authorities have no information other than that a mechanical malfunction - and not a terrorist attack - brought down the plane.

A law enforcement source at the scene told The Associated Press that the likelihood of a mechanical problem stemmed from the fact that flames were seen shooting out of the left engine and that witnesses reported the plane had difficulty climbing and was banking to the left.

Jet engines have been known to break up catastrophically, throwing shrapnel through a plane. In 1989, United Airlines DC-10 crashed in Sioux City, Iowa, killing 112 people, after the metal hub that holds the engine's fan blades shattered and ruptured the jet's hydraulic lines.

In 1996, an engine fan hub ruptured on a Delta flight as it rolled down the runway for takeoff, sending shrapnel into the passenger cabin that killed a woman and her 12-year-old son.

The NTSB said investigators recovered the Airbus flight data recorder, one of the jetliner's two "black boxes."

In Washington, President Bush met with advisers, seeking details of the crash. A US official, speaking on condition of anonymity, said intelligence agencies, the FBI and the Federal Aviation Administration were reviewing all recent intelligence for any signs that terrorism was involved.

Giuliani canceled his morning events and headed to the scene, where he said: "People should remain calm. We're just being tested one more time and we're going pass this test, too."

"Now we should focus all our efforts on finding survivors," Giuliani said.

"The first thing that went through my mind is, `Oh, my God.' I just passed the church in which I've been to, I think, 10 funerals here. Rockaway was particularly hard hit. The disproportionate number of the people we lost - not just the police and fire, but even the workers at the World Trade Center - were from Rockaway and Staten Island."

Triage centers were set up a high school and an elementary school, both of which were closed for the Veterans Day holiday.

A hospital near the crash site said it treated about 15 people for smoke inhalation and several others for abrasions. All of the injured had been on the ground, not the plane, and none appeared to be critically injured.

The plane was lying on top of about 12 homes, said Ed Williams, community liaison for Rep. Gregory Meeks. "It's pandemonium here," Williams said. "We don't know if there are any survivors but it looks really bad."

"This community was hit so hard by the Trade Center," said Fern Liberman, who lives a few blocks away. "A lot of firefighters, policemen and we had a lot of people at Cantor Fitzgerald. We were hit very hard. ... Just on the heels of one horror, another."

The plane had been scheduled to leave at 8 am and arrive in Santo Domingo at 12:48 pm According to the FAA, it took off at 9:14 am and crashed three minutes later.

"First I heard a big explosion. then I saw flames come out from behind the plane. And then a whole wing with the engine fell off," said Antonio Villela, a construction worker.

Witness Phyllis Paul said she heard the plane's engine. "It was very, very loud. Because of what happened Sept. 11, it gave me a chill," she told CNN. "It was getting louder and louder and I looked out the window. I saw a piece of metal falling from the sky."

Jackie Weiss, 50, a secretary at Rockaway High School, said an engine fell on a house down the street from hers.

"I'm really devastated," she said. "My own son was telling me, when I was upset by the World Trade Center, `But you didn't lose any family members.' But seeing something like this ... I feel the world is coming to an end."

In the Dominican Republic, relatives of passengers crowded Santo Domingo's airport, sobbing and grasping each other after hearing about the crash.

"Oh my God!" said Miriam Fajardo, crying after being told that her sister and three nephews were aboard. "I hadn't seen them in eight years. Now they're gone."

The Trade Center was destroyed by two Boeing 767s hijacked out of Boston's Logan Airport. One of the planes was operated by American, the other by United.

Airbus said American Airlines has a fleet of 35 A300s.

In 1996, TWA Flight 800 left Kennedy Airport for Paris and crashed off Long Island, killing all 230 people aboard. The NTSB concluded the jet was destroyed by a fuel tank explosion, probably caused by a wiring spark.

(China Daily November 13, 2001)