Authorities sought to determine whether foul play caused the tragedy, which saw the Cairo-bound aircraft plummet into the ocean just 33 minutes after taking off from New York, according to officials who cited radar reports.As night fell over the crash scene off the US east coast, officials scaled back what they were still calling a search-and-rescue operation.

So far, those efforts have only yielded one body, some human remains and sundry wreckage from the debris field roughly 100 km southeast of Nantucket Island, Massachusetts.

``We found a wheel, life rafts that were partially inflated, portions of seats, clothing and some paperwork including passports,'' Rear Admiral Richard Larrabee of the US Coast Guard told a Boston press conference.

The cause of the disaster, which occurred in clear weatherafter the Boeing left New York's John F. Kennedy airport at 1:19 a.m. was unknown said Jim Hall, chairman of the National Transportation Safety Board which coordinates crash investigations.

``We will undoubtedly hear many reports on what might have caused the crash of flight 990. All of those reports will be speculative. We do not know at this point wh at caused the crash,'' he told a Washington news conference.Search efforts were ``downgraded'' by nightfall, with helicopters and aircraft to be ``pulled back'', leaving only four naval vessels at the site, he said.

In Washington, US Transportation Secretary Rodney Slater said federal officials would provide any assistance needed in the recovery effort. Among the assistance provided by authorities is the US Navy ship USS Grapple, equipped with highly sophisticated sonar, which left its base in Norfolk, Virginia for the Atlantic Ocean wreck site. The Grapple could prove critical in locating the wreckage which is believed to be submerged in 65-80 m ofwater.The plane was carrying 197 adult passengers, two children not occupying seats, 15 crew on duty and three off duty when Flight 990 vanished from radar screens.

Last contact with the pilots was at 1:47 a.M. 28 minutes into the flight and was ``routine'', Hall said. Three minutes later something went tragically wrong.

``The airplane began a descent from 33,000 feet at about 1:50 a.m.,'' Hall said. ``The last radar contact in which the airplane provided altitude data was about 36 seconds later. At that time the airplane had descended to 19,100 feet a very rapid descent, approximately 23,200 feet per minute.'' Two minutes later the plane disappeared, Hall said.

Egyptian Transport Minister Ibrahim al-Dumeiri said 129 US nationals and 62 Egyptians were among those aboard. Early reports said there were also two Sudanese, three Syrians, and one Chilean. Meanwhile, experts were studying radar information to determine whether the plane had broken up before hitting the water.