Egyptian government officials yesterday challenged the National Transportation Safety Board's plan to launch an FBI-led criminal probe into the fatal crash of EgyptAir Flight 990, arguing that there isn't enough evidence to assume the crew intentionally downed the plane.

NTSB officials were ready to hand over the investigation to the FBI after hearing on the voice recorder what they think is one of the pilots, who apparently was alone in the cockpit, say a prayer in Arabic before turning off the plane's autopilot and forcing the jet into a dive, sources familiar with the probe said. And safety board chairman Jim Hall said that, based on evidence so far, no mechanical or weather problem could have caused the crash.

But the Egyptian government suggested alternative interpretations of the crew members' actions and the religious phrase. Egyptian officials asked to have their own experts review the voice and flight data recorder tapes before the FBI takes over the case, said Hall at a news conference late yesterday. One of them, an envoy from Egyptian President Hosni Mubarak, arrived in Washington yesterday.

An Arab official in Washington stressed that there is no conflict between Egypt and the United States but added: "We don't feel there is enough evidence to warrant turning it over to the FBI."

At the often-delayed news conference, Hall said the decision to hand over the probe to the FBI "cannot be made lightly."

"It is only prudent for the National Transportation Safety Board to consult with these experts and officials prior to any final decision . . . about whether this should be transferred to the bureau," Hall said.

The FBI had prepared to take charge of the investigation during most of the day, with Director Louis J. Freeh briefing congressional leaders about the evidence that had prompted federal officials to think a criminal inquiry was appropriate.

A possible motive for deliberately crashing the plane remained unclear yesterday, officials said. FBI agents, with the assistance of Egyptian officials, are conducting interviews with family members and others and trying to understand what factors could have led someone to take the plane into a deadly plunge.

Part of their focus is on the lives of the four assigned crew members who could have been at the controls when the plane started its dive. Reports about one of the four--Flight Officer Gameel Batouti--suggest that he had recent personal problems related to his young daughter's health.

His daughter, about 8 years old, is battling a serious illness and is being treated at UCLA Medical Center in Los Angeles by a rheumatologist. Officials there declined to name the disease yesterday but said that she has spent substantial time at the medical center in the last year or so and in recent months has shown marked improvement. The daughter is not under full-time care at the hospital, officials said, but receives her medical treatments as an outpatient.

Investigators believed they had a good idea who was in the cockpit at the time of the dive but now are less certain. Sources close to the investigation point out that at least eight people aboard the plane could have flown it--four flight crew members and four pilots who were riding in the cabin as passengers.

Normally only two flight deck crew members are required to fly a 767, but on lengthy flights one or two pilots will be added to allow everyone to have some rest. The lengthy New York-Cairo flight apparently required a total of four pilots.

More details emerged about the final conversation of the flight's crew and the sequence of events surrounding their words. Government sources cautioned that these early findings are preliminary. The Oct. 31 crash off the Massachusetts coast ultimately killed all 217 of the passengers and crew members on board.

The prayer offered by the pilot at the controls was "suggestive of somebody who is about to take some significant action of some kind," one expert familiar with the tape said.

"It is the kind of thing one would say before you took some significant action. . . . You are trusting in God to provide guidance or putting your fate in God's hands. There is not a mention of death," one source familiar with the tape said.

In addition to the FBI and safety board officials, CIA language specialists, Egyptian government officials and State Department experts have all been involved in discussions about the review of the tape and the crash in recent days.

While nothing on the tape indicates a physical struggle between the co-pilot and the pilot, the voice and data recorders suggest that at some point they were working at cross purposes in an effort to control the aircraft. After the plane's plunge had begun, its left and right elevators--which help the plane raise and lower altitude--split, with one going up and one going down. These plates at the rear of the horizontal stabilizer normally operate in tandem, making the plane climb or descend. They are designed to split from each other if the two pilot's control columns are pushed in opposite directions with at least 50 pounds of force.

"There were two guys trying to fly this in opposite directions," one source familiar with the matter said. According to the data recorder, the plane had climbed to its cruising altitude of 33,000 feet before the flight's autopilot was switched off. After its descent began, the plane rapidly plunged to 16,000 feet, before climbing to 24,000 feet and then stalling before its final plunge into the ocean.

Unlike the crash of TWA Flight 800 three years ago, there were no eyewitnesses to the EgyptAir crash, giving the FBI a lower profile in the early weeks of the investigation. When the TWA flight crashed, there were numerous people on Long Island who said they saw streaks of light that could have been a missile, though that was never proven.

Nevertheless, the FBI has had 250 to 300 agents working on the EgyptAir crash in the last couple of weeks, according to FBI spokesman Joseph A. Valiquette. "We had evidence technicians on the boats in both cases, who are examining the debris as it comes in and maintaining the chain of custody under the federal rules of criminal procedure in case the investigation did go criminal," Valiquette said.

Staff writers Don Phillips, Vernon Loeb, John F. Harris, Rene Sanchez, Howard Schneider and Nora Boustany and staff researcher Alice Crites contributed to this report.

CAPTION: A DIVE, RECOVERY, A SECOND PLUNGE (This graphic was not available)

CAPTION: NTSB Chairman Jim Hall at end of news conference. Based on evidence so far, he said, neither mechanical nor weather problems contributed to crash.

CAPTION: NTSB Chairman Jim Hall said Egyptian officials want a chance for their experts to review the tapes.