NEW YORK (AFP) - Investigators were sifting through the wreckage today for more clues to the cause of the crash here of an American Airlines jetliner that killed all 260 aboard and a few people on the ground.

American Flight 587, an Airbus A300 bound for Santo Domingo, had slammed into a residential area of New York yesterday, destroying homes and igniting new fear in a city traumatized by September's terror attacks.

Six people on the ground were reported missing.

Speculation immediately centered on a possible new terror attack. City authorities ordered a huge security alert, as military jets flew air cover and city bridges, tunnels and airports were closed.

But the National Transportation Safety Board said early signs pointed to a catastrophic mechanical failure on board the plane because the engine appeared to fall off and because the crash happened so early in flight.

Investigators have already recovered the plane's cockpit voice recorder and have sent it to be analyzed by experts in Washington.

Voices of pilots

NTSB chairman Marion Blakey said that the only voices heard were those of the pilot and co-pilot. "The NTSB is the lead agency because all the information we have currently is that this is an accident," she said.

The Federal Bureau of Investigation would take over the probe if criminal intent were suspected.

By late Monday, searchers had recovered 265 "relatively intact bodies," CNN quoted police as saying.

Thick black smoke belched into the air after the plane hit, spoiling the brilliant clear morning.

Shards of burning wreckage littered tree-lined residential streets, while fire consumed houses bathed in aviation fuel. The tail section of the plane was later pulled from nearby Jamaica Bay.

Twelve houses were hit, including four which were destroyed, Mayor Rudolph Giuliani said. One was damaged when an engine of the doomed plane, almost intact, sliced into it. Other wreckage just missed a gas station.

Workhorse equipment

Eyewitness reports suggested an engine had tumbled from the plane before it crashed.

Fearing a new wave of terror, Giuliani immediately put the city on high alert, two months after hijackers turned airliners into flying bombs and destroyed the city's landmark World Trade Center.

The White House said there were "no unusual communications" between the twin-engine jet and air traffic controllers before the crash.

New York Governor George Pataki said the pilot had dumped fuel before the disaster, but later said reports to that effect were inconclusive.

President George W Bush expressed condolences to the families of the dead.

"The New York people have suffered mightily, they're suffering again. But there is no doubt in my mind that New Yorkers are resilient and strong and courageous," Bush said.

American Airlines said 251 passengers and nine crew members were on board the plane, including five infants carried on their parents' laps.

"American Airlines will not speculate as to possible causes of the accident. At this point, no additional details can be confirmed," a statement said.

Anguished relatives

In Santo Domingo, 500 anguished relatives of passengers on the plane waited for information. Dominican President Hipolito Mejia lamented "any event that results in the loss of a single human life" and authorities declared three days of mourning.

Neighboring Cuba was among a host of nations to send condolences to the United States and the Dominican Republic late yesterday in the wake of the crash.

A Cuban television presenter made the announcement before a program detailing the air disaster, without revealing the text of the message.

Many of the dead aboard the plane were thought to be Dominicans returning home.

And while dignitaries, including New York's mayor elect Michael Bloomberg, gathered at northern Manhattan's Dominican Sports Club late yesterday to pay homage to the dead, around 200 people stood outside, next to an improvised altar of candles, plastic hibiscus and a nativity poster, surrounded by Dominican and US flags.

"We've barely begun to recover from the shock of the Sept 11 tragedy and now this," lamented Dominican Ambassador Luis Edulis Perez, tears in his eyes.

Workhorse equipment

Flight 587 left Kennedy at 9.14 am (1414 GMT), and radio contact was lost three minutes later, FAA spokesman Paul Takemoto said.

The aircraft, a French-made, Airbus A300-600 with the capacity to hold 266 passengers, was delivered new to American Airlines in July 1988, and was powered by two General Electric CF6-80C2A5 turbofan engines, Airbus said in a statement.

The aircraft and its engines are generally considered workhorse equipment with few safety problems given their widespread use.

However, concerns about the safety of the General Electric engines have emerged from recent incidents, leading the FAA in August 2000 to order more frequent inspections for cracks in the high-pressure turbine discs and to further tighten the requirements in June.

"We are not aware of any operational issues that would have endangered the aircraft at this point," GE spokesman William Kennedy said yesterday in response to the crash.

One of the two engines on the Airbus that crashed had gone 9,788 hours since its last overhaul, while the other had gone 694, said American spokesman Al Becker.

Hijacked airliners

Overhauls are supposed to be conducted every 10,000 hours, he said.

On city streets, bewildered citizens, still coming to terms with the deadly Sept 11 attacks, in which hijacked airliners collapsed the World Trade Center, gathered around televisions in shops, and police officers seeking early details about the crash.

The United Nations building where the UN General Assembly annual debate is taking place was immediately sealed off and the Security Council stood in silence for one minute in tribute to the victims.

Giuliani said the Rockaway waterfront area where the plane went down had been badly hit by the World Trade Center disaster.

"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," he said.

Senator Charles Schumer added: "It just cuts your heart in half ... this is a small town in a big city, people look out for each other. One wonders what this is all about and what God means by all this."

Stocks fell sharply after the crash but later recouped most of their losses.