NEWPORT, R.I. - Coast Guard crews searching for clues in the crash of EgyptAir Flight 990 found the first large piece of wreckage Monday and detected a signal believed to be from one of the plane's ''black boxes.''
About 80 grieving relatives arrived in Rhode Island as the Pentagon revealed that 30 Egyptian military officers were on board. Among the officers was at least one brigadier general, according to administration officials speaking on condition of anonymity.
Because terrorism has not been ruled out, the FBI said it is sending bomb experts and other investigators to Newport. But authorities stressed there was no evidence of foul play.
''Nothing has been ruled in, nothing has been ruled out,'' President Clinton said in Oslo, Norway, where he was attending Middle East peace talks.
Jim Hall, chairman of the National Transportation Safety Board, cautioned that the investigation - already involving more than 500 people - could be long. And he said the hunt for the black boxes - the flight data recorder and cockpit voice recorder - would be difficult.
''Remember that we are dealing with water 250 feet deep, and recovering and locating small objects like recorders is a daunting effort,'' he said at search headquarters in Newport.
The Cairo-bound Boeing 767 was carrying 217 people when it plunged into the Atlantic from 33,000 feet early Sunday, a half-hour after leaving New York's Kennedy Airport. The plane went down without a distress call or any other indication of trouble from the pilots.
The Egyptian military officers were mostly pilots who had been training in the United States, the Pentagon said. The passengers also included 106 Americans - 54 people bound for a two-week trip to Egypt and the Nile.
The first group of victims' relatives arrived from New York Monday afternoon by chartered plane at T.F. Green Airport in Warwick, where they were greeted on the tarmac by an Egyptian priest. They were taken to a hotel and offered grief counseling from the Red Cross and other organizations.
George Arian, a friend of one of the victims and owner of an Arabic newspaper in Jersey City, N.J., was on the flight to Rhode Island and said some passengers panicked briefly as the plane began flying over water soon after takeoff.
''It was a shock. Some people were crying hard,'' Arian said. ''Every lady or every man was thinking of his loved one.''
The debris collected so far - some of it by student sailors from the U.S. Merchant Marine Academy - includes shoes, purses and teddy bears.
''It basically looked like somebody had emptied their trash Dumpster,'' said one of sailors, Chris Kincaid.
None of the retrieved debris has any burn marks that might indicate a fire or explosion, search officials said.
The Coast Guard, fearing bad weather on Tuesday, stepped up its search for debris and human remains. Officials admitted a new phase of the operation had begun.
''It is in everyone's best interest to no longer expect we will find survivors,'' said Coast Guard Rear Adm. Richard M. Larrabee.
Larrabee, speaking 35 hours after the crash, said the decision was based partly on the chilly water. The average life expectancy in water of 58 degrees is five to six hours.
Searchers found what Larrabee called a ''significant piece'' of the aircraft, large enough to require a crane. They also located a signal, most likely one of the plane's black boxes, while scouring the search area south of Nantucket.
The Navy will use underwater sonar equipment to try to pinpoint the wreckage and the black boxes. The USS Grapple, a sonar-equipped salvage ship that helped retrieve wreckage from the 1996 crash of TWA Flight 800 off Long Island and the 1998 crash of Swissair Flight 111 off Nova Scotia, was expected to arrive from Virginia on Tuesday.
''We have a very difficult job in terms of the recovery ahead,'' said Hall, noting that Flight 990 crashed in water twice as deep as Flight 800.
As of midday Monday, only one body had been recovered, but Larrabee said searchers had ''begun to see evidence of further human remains.'' He would not elaborate.
Flights were being arranged to carry victims' relatives to Rhode Island so they could be close to the search operation. Dozens of grief counselors from the Red Cross and other organizations were on hand.
Some of the human remains, and aircraft debris such as evacuation slides and life preservers, were brought to the Quonset Point Naval base near Newport.
After the crash, investigators were sent to check on the EgyptAir ground crew at Kennedy.
''As far as my knowledge goes, everyone seems to have checked out and everyone cooperated,'' said Robert Kelly, general manager of aviation for the Port Authority of New York and New Jersey, which operates the airport.
The plane's co-pilot, Adel Anwar, had been on his way back to Egypt to get married on Friday. Eager to help with wedding preparations, he had swapped shifts and took a colleague's place in the cockpit that fateful night.
''It was just another regular flight,'' Anwar's tearful brother, Tarek, said in Cairo. ''Or so we thought.''