The Maltese government today backed away from its earlier description of the Egyptian assault on the hijacked Egyptair jetliner, saying that its accounts until now had been based on initial reports from the plane's Egyptian pilot and not on independent Maltese investigations.

The truth about the hijacking of Egyptair's flight 648 last Saturday and the bloodshed during the Egyptian commando attack on the plane 24 hours later, would be established only after an investigation now under way by Maltese magistrate Noel Cuschieri, government spokesman Paul Mifsud said.

His remarks, in an interview, came as the government imposed a news blackout on information about the one alleged hijacker who survived and as evidence mounted that most of the 57 persons killed in the rescue operation Sunday died from smoke inhalation caused by bombs used by the Egyptian commandos when they stormed the plane.

The original report from Egyptian authorities, initially accepted by the Maltese government, alleged that the number of dead from the Egyptian operation had resulted from hand grenades thrown by the hijackers when the commando raid began and the grenades started a fire that swept through the plane.

"The magistrate will definitely inquire into when they the Egyptians went in, how they placed the bomb, everything," Mifsud said when asked about the growing evidence that the majority of the deaths in the rescue attempt had been caused by the Egyptians, not the hijackers, as originally stated by Maltese and Egyptian authorities, including President Hosni Mubarak.

Mifsud's statement came as a Maltese coroner, Dr. Abela Medici, aided by an American pathologist who arrived here Tuesday at the behest of the U.S. Embassy, completed their autopsies of the 57 corpses taken out of the plane and the two bodies of passengers killed by the hijackers before the raid. Fifty-nine of the plane's 98 passengers, crew and hijackers died during the 24-hour hijacking.

Interviewed at the Malta University anatomy laboratory today, Medici said that the main causes of death of those bodies that he had examined were asphyxiation and "some" bullet wounds.

Asked to confirm reports from Professor Angelo Pfaila, the head of medicine from St. Luke's Hospital, where survivors are recovering, that most of those in his care suffered from smoke inhalation, Medici said of the dead, "Let's just say there was a lot of smoke in the plane."

Medici, who said he could not be more specific because of the need to maintain judicial secrecy of the Maltese magistrate's investigation, would not comment directly on the reports that the Egyptian bombs had created the smoke that killed and injured so many.

"We are still investigating that," the doctor said. "That is something I would like to keep for later."

Medici indicated that few of the victims had died of burns -- a fact that seemed in conflict with claims by Mubarak that the hijackers had thrown phosphorous hand grenades. The pilot, Hani Galal, had reported that the hijackers were brandishing hand grenades.

To date, no evidence has emerged here that phosphorus grenades were used, and there have been no reports of flesh burns or the distinctive white ash that accompanies phosphorus explosions.

On the contrary, persons close to the investigation increasingly believe that what caused the fire in the plane and the thick, white smoke that poured through the cabin after the Egyptians stormed the aircraft was the bomb that the Egyptians used in their attack.

It remains unclear whether it was the initial bomb that the Egyptians planted in the rear cargo hold of the plane to blast through the passenger cabin floor or smoke bombs thrown later, apparently to blind the hijackers, that caused the fires and smoke that now appear to have caused most of the deaths.

One theory under investigation is that the initial big explosion in the cargo hold was the cause of the fire, igniting the cabin's plastic walls and ceiling. Another theory is that it was the smoke bombs, normally designed for outdoor use, that asphyxiated the passengers.

There seems to be little doubt that the fire and smoke started in the rear of the plane, the main entry point of the Egyptian commandos.

The sergeant in the fire department of the community of Corrandino, near the airport, who rushed to the scene to help airport firefighters, said in an interview today that the fire and smoke was "mainly in the back of the plane, over the cargo hold."

"There was a lot of smoke," the sergeant said, "but not that much fire."

Witnesses who had seen the plane from a distance immediately after the Egyptian attack began, recall seeing no flames at all but thick, white smoke billowing through the front doors and cockpit windows.

The plane remains intact, its inside cabin charred, but the white paint on its fuselage unblistered, except for a scorched 20-foot segment of the fuselage roof immediately over the rear passenger compartment and the cargo bay, where the Egyptians entered.

Meanwhile, the government has imposed total secrecy on the one wounded alleged hijacker in its custody

Spokesman Mifsud said the government would have nothing more to say about the alleged hijacker until the investigating magistrate released his report, citing the need to maintain tight security.

The remaining mystery in this hijacking remains the identity of the three hijackers who took over the plane in the name of the nebulous Egyptian Revolutionary Organization, a group whose only other claimed exploit was the assassination of an Israeli diplomat in Cairo last summer.

Two hijackers, who apparently had used Moroccan passports, were killed in the hijacking or the raid thereafter, and nothing has been learned about them, according to sources here. The wounded hijacker, who traveled with a Tunisian passport under the name of Omar Marzouki, apparently has said very little since emerging from anesthesia after an operation for bullet wounds in his lung. All he has said, according to Maltese authorities, is that he is Tunisian.

The airliner's crew, all Egyptians, have been unanimous in doubting that the hijackers are Egyptian because their accents sounded more Palestinian or Lebanese. But the theory that the hijackers were dissident Palestinians is discounted by Arab and western diplomats here because the hijackers behaved so uncharacteristically and kept on board two Palestinian families, including eight children, who later died.

The body of Scarlett Marie Rogenkamp was put aboard a plane for Oceanside, Calif., after a 15-minute ceremony at the airport attended by U.S. Ambassador Gary Matthews, The Associated Press reported. According to passengers' accounts, Rogenkamp was one of five passengers shot by the hijackers before the Egyptian assault.