The swiftness of the jumbo jet's mid-air destruction, the broad swath of the Atlantic Ocean littered by debris and the absence of an emergency call for help has led investigators to focus on the possibility that TWA Flight 800 was knocked from the sky by terrorists.

Even as they cautioned against premature conclusions, federal, state and local investigators were exploring every scenario from whether a bomb exploded in the plane to whether a missile fired from the ground picked it from the air. If confirmed, it would be the deadliest terrorist attack in American territory ever.

But the prospect of a catastrophic mechanical failure also remained. Evidence culled from the gruesome retrieval of more than 100 bodies and wreckage from the waters off the South Shore also puzzled investigators because initial inspections turned up no telltale signs of shrapnel or powder.

All that was clear was that all 230 people on board the Boeing 747 bound for Paris perished in the explosion or by drowning in the water below, spreading grief among friends and family across at least two continents.

"It's just a senseless waste of two people," said Richard Hammer of Long Beach, whose wife, Beverly, 59, and daughter, Tracy Anne, 29, were on the flight. "You can't make sense out of it. You take two people at the top of their game and literally wipe them out. I'm stunned."

Stunned too were officials at all levels of government. For part of the day, the National Transportation Safety Board and the Federal Bureau of Investigation struggled for control of the case, and New York City Mayor Rudolph Giuliani wrangled with TWA officials. Gov. George Pataki flew over the crash site and later hugged victims' families, then said, "It's the worst thing I've ever seen."

On a placid summer sea, meanwhile, a small navy of boats dispatched by federal and local authorities continued throughout the day and into the night the grisly task of filtering the wreckage and human remains still floating in the water.

As debris drifted slowly east with the current, divers had to pick through everything from a red TWA flight bag to a child's purple backpack emblazoned with Barney the Dinosaur. Investigators were using radio waves to seek the plane's "black box," which could indicate if an explosion ignited the fireball.

The Coast Guard was able to recover plane debris ranging from hundreds of small parts to a 30-foot piece of the wing, which could prove critical, officials and aviation experts said, because the markings on the metal could confirm whether the plane was blown up, and if so, with what type of bomb.

The pieces were being brought to the former Grumman facility in Calverton for examination. Experts who helped collect evidence after a ValuJet plane went down in the Everglades May 11 and after a Pan Am flight was blown up over Lockerbie, Scotland, in December, 1988, were brought in to help with the search.

Government officials, both civil and criminal, said they were seriously examining the possibility that a missile struck the plane, because of an apparent blip on the screen before the explosion. The blip, if not a meaningless shadow, could conform to what some investigators said were accounts of a flash rising from the surface before the blast.

But electronic clutter on the tapes is making a determination difficult, the officials said. And the plane was believed to be outside the range of most shoulder-launched missiles. As one intelligence official said, "We can't rule anything out at this point. But the missile wouldn't be all the way up there on the probability list."

White House press secretary Mike McCurry said investigators were "trying to clarify any abnormalities" that turned up on radar screens. Asked about speculation on a missile, McCurry replied, "There's no American official with half a brain who ought to be speculating on anything of that nature. There's no concrete information that would lead any of us in the United States government to draw that kind of conclusion."

Officials were also quick to caution that the circumstantial evidence of an attack does not rule out a mechanical failure. In both 1991 and 1992, an early model 747 jet had crashed shortly after take-off when an in-board engine fell off the plane and then tore off the outboard engine on the same wing.

"I wouldn't be surprised if it turns out this has been a horrible accident," one source familiar with the investigation at the site said. But sources conceded that they may not have recovered those parts of the plane or the bodies that could show blast damage.

In the absence of explanations, theories abounded. One focused on a fax sent Wednesday to an Arabic language newspaper in Beirut warning of an attack. State Department and CIA officials confirmed they had received copies of the fax Thursday.

The message said "tomorrow morning we will strike the Americans in a way they do not expect and it will be very surprising to them," according to one official. A counterterrorism source familiar with the fax said that it was sent at 11 a.m. New York time Wednesday, more than nine hours before the bombing. But a CIA source said that the agency "does not attach too much significance" to the fax.

Another key sign that investigators were looking at Thursday was whether the metal in the wreckage was twisted outward, which would suggest an explosion like one caused by a bomb from inside the plane, or twisted inward, which might suggest that an engine or a missile had exploded outside.

"If there was an explosion, there will be very specific, telltale signs by the way it explodes, the damage to the airplane, and the residue left," said Dick Stone, who heads the Virginia-based International Society of Air Safety Investigators.

Recovering bodies also remained a top priority. By last night, remains of 140 of the 230 people TWA officials said were on the flight had been fished from the water. The bodies were placed on Coast Guard cutters whose decks were stained with blood, then brought by smaller boats to a makeshift morgue at the command center in East Moriches.

The remains were often badly burned and mangled beyond recognition. One was just a charred torso with no arms, legs or head, another's clothes and hair were burned off, and a third was a woman still wearing a black dress and a gold necklace.

"I was telling the guys these aren't people anymore, they're just bodies. The people are gone," said John Rich, 28, a Coast Guard petty officer. "Some of the guys out here are pretty young, 19 or 20 years old, and they've never seen anything like this. I told them to just mentally block it out. They handled it pretty well. But I'm sure when it's all over, that's when it's really going to hit them."

When the bodies first arrived at the morgue, investigators opened each body bag only long enough to take photographs and note identifying characteristics or jewelry before they were moved to refrigerated trucks.

Officials said X-rays will be taken of each body to search for shrapnel or other evidence of a bomb. "We're looking for things like that, missiles or projectiles that are embedded in a body," said Dr. Charles V. Wetli, the chief medical examiner for Suffolk County.

But Wetli said the first 20 autopsies turned up no evidence of any kind of explosive, nor any powder residue. Some of the victims had drowned, he added, though they were believed to be unconscious when they hit the water.

Yet many more corpses still remained in the ocean late Thursday, and divers and emergency workers on the boats described the search in waters 120 feet deep and about 10 miles from shore as gut-wrenching.

"It's a grim task," said Raymond Tremer, a diver with the New York City Fire Department team at the scene. "We aren't sure what we are going to find. We suspect that the passengers are seat-belted into the fuselage. It's a difficult situation because you have to enter the fuselage. There are cable and wires there."

By evening, there were also scattered reports that sharks might be in the area, and the search is likely to get harder still as clear skies are replaced by thunderstorms and showers today.

For the families awaiting what seemed almost inevitably negative news Thursday, the day was worse still. After a restless night during which top TWA officials were hard to find at Kennedy, the families sought news at daybreak.

But for hours, TWA refused to release the full list of people on the plane. The airline revised the number of people said to be on the plane twice during the day before settling on the figure of 230, including 212 passengers, 14 flight attendants and four crew members in the cockpit.

Mark Abels, a TWA spokesman, said the airline wanted to notify all the families before releasing the list. But even after relatives gathered at the Ramada Inn near Kennedy Thursday afternoon, no list was released, and Giuliani engaged in a nose-to-nose shouting match with one TWA official about the delay.

Frank Capozza, a New Jersey man waiting at Kennedy who had put an 11-year-old French exchange student on the plane Wednesday night, erupted at the wait. Capozza, who wanted someone to call the child's parents in France, walked over to another TWA employee standing nearby and said, "This is wholly out of control. Don't you have a system? You have people here that don't know anything. Talk about a low-rent airline."

Although TWA released the list at 8:24 p.m., the clash raised anew questions over whether airlines - which face liability and public relations threats after an air disaster - are equipped to deal with families after plane crashes or whether government entities should assume control. But TWA officials defended their handling of the incident.

"Like ... [Giuliani], we regret that the notification process took so long," said Abels.

During the day, most family members and friends at Kennedy and elsewhere were more subdued. Many concluded that almost everybody expected to be on the flight - people such as Eric and Virginia Holst of Manorville, who were headed to a family wedding in France, and Jacques and Connie Charbonnier, married flight attendants happy to work the same flight - must have perished.

And TWA did release the names of the cockpit crew early in the day. The airline identified the four men as the pilot, including Capt. Steven Snyder, 57, of Stratford, Conn., who had been with TWA since 1964.

Friends said Snyder was a "master pilot" who had just paid for a complete overhaul of his own single-engine Cessna.

"He called it his pet," said Stanley Loban, a fellow small-plane flier. "He got more of a kick out of the little one than the big one."

A small number of families unexpectedly heard good news Thursday. On Wednesday night, Jose Fermin was running frantically through Kennedy, saying that his mother was "crying and crying" because his brother, Alberto, of Brooklyn, was booked on Flight 800, headed for a French vacation. Thursday, however, the Fermins were euphoric after learning Alberto had taken a Tower Air flight to Paris instead.

Eileen Remce of Appleton, Wisc., was also marveling at her good fortune. Her connecting flight from Chicago had been delayed, and even though she arrived at Kennedy about 15 minutes before Flight 800 departed, officials refused to seat her.

"I guess I cheated the grim reaper," said Remce, who called her family, and told her younger daughter that she had missed the plane. But Remce nonetheless planned to get another TWA flight to Paris last night. "Is that stupid or what?" she said.

As the day wore on Thursday, officials and experts increasingly devoted attention to the possibility that the explosion on the plane was caused by a bomb.

The practical reason for arriving at that conclusion was the fact that Flight 800 disappeared from FAA screens suddenly and without warning, according to officials close to the case. Even in the ValuJet crash, the crew had time to transmit calls for emergency aid.

"Either something happened quickly, like the wing tore off and exploded - which has never happened - or a device went off ... airplanes do not blow up suddenly in flight," said one official.

Many other explanations were dismissed by aviation experts. Weather was not a factor, because the skies were clear. As it climbed to about 13,800 feet, there were no mountains or other physical barriers the plane could have struck. And a collision with another plane would be unlikely, considering the sophisticated navigation equipment on planes.

Nor did the plane's crew indicate any problem to the three traffic control centers that handled the flight between the time it left the runway and it disappeared from the screens of controllers in Nashua, N.H. "When a controller sees [an airplane] disappear on the screen, you know either you have a radar problem or you have a disaster on your hands," said an FAA spokesman.

If terrorists did down Wednesday's flight, it would not be the first such attack on a plane within American territory, with previous episodes dating back to 1933, when seven people died after a bomb exploded on a plane in Palm Springs, Calif.

But if terrorists are responsible, they caused more deaths than any other such attack within U.S. territory. The terrorist act currently considered the nation's deadliest was last year's Oklahoma City blast, which killed 169.

This story was reported by Michael Arena, Al Baker, Deborah Barfield, Bill Bleyer, Emi Endo, Martin C. Evans, Ford Fessenden, Ken Fireman, Andrew Friedman, Mitchell Freedman, Craig Gordon, Katti Gray, Isaac Guzman, Joe Haberstroh, Carol Hernandez, Glenn Kessler, Robert E. Kessler, Jessica Kowal, Earl Lane, Jerry Markon, Molly McCarthy, Nora McCarthy, Phil Mintz, Geoffrey Mohan, Elizabeth Moore, Samson Mulugeta, Soraya Sarhaddi Nelson, Shirley E. Perlman, Joseph W. Queen, Jordan Rau, Knute Royce, Sidney C. Schaer, Gaylord Shaw, Michael Slackman, Patrick J. Sloyan, Andrew Smith, Lauren Terrazzano, James Toedtman, Robin Topping, Beth Whitehouse, Steve Wick, Olivia Winslow and Ellen Yan. It was written by Liam Pleven.