Many of the 57 persons who died during an Egyptian commando raid against a hijacked Egyptair airliner last weekend appeared to have been killed by a powerful bomb the Egyptians used to enter the plane, according to reliable sources close to the investigation.

The report that it was an Egyptian bomb and ensuing fire, not grenades thrown by the hijackers, that caused many -- and possibly the majority -- of the deaths contradicted early reports by Maltese officials and Egyptian President Hosni Mubarak. Sources familiar with the autopsies being performed on the victims said their wounds were consistent with a much stronger blast than could have been caused by the hijackers' grenades.

According to the sources close to the investigation, the evidence indicates that the Egyptians used a "much too powerful bomb" in a cargo hold, directly below the passengers sitting at the rear of the plane, to gain access to the cabin. Several smaller bombs may also have been thrown by the Egyptians, the sources said.

The report is consistent with the recollections of witnesses who saw the commando raid from the airport control tower and recalled a "big bang" that shook windows up to a mile away and caused a lightning flash. Small-arms fire was reported to have followed for "more than a minute." Mubarak said yesterday that his commandos had fired only seven shots in the operation.

The power of the bomb is evident from a close scrutiny of the damaged Boeing 737 on the isolated parking apron where it was assaulted Sunday. During that time the hijackers shot three American and two Israeli passengers. One, American Scarlett Rogenkamp, was killed, and a second, an Israeli woman, remains alive but declared clinically dead. The other three, two Americans and one Israeli, survived. The hijackers also wounded one Egyptian security guard and two Egyptian flight attendants before the plane touched down here Saturday night.

The rear cargo door, which had been opened before the assault began, hangs from twisted hinges, nearly blown off from the inside. Paint on the roof of the plane immediately over the rear cargo compartment and the passenger area is scorched, apparently by the explosion.

Despite a new claim by Mubarak yesterday that the hijackers had started the fire with phosphorus grenades rather than the "high-intensity grenades" that pilot Hani Galal said hijackers were brandishing, doctors have reported no phosphorus burns among the wounded. Nor have investigators who searched the the plane reported the white ash and burn marks characteristic of phosphorus explosions.

Passengers recuperating in the island's St. Luke Hospital almost all were seated at the front of the plane or the midsection, near the emergency hatches over the plane's wings that the Egyptians also used to enter the aircraft.

"I think all of us who survived were those toward the front of the plane," said Anthony Lyons, an Australian marketing consultant, who was in seat 2B.

Lyons also corroborated the reports of heavy Egyptian firing inside and outside the plane. He said that when the raid began, he got down on his stomach and crawled up the aisle toward the front door, crawling over a body, then slithering outside on a landing stairway on his belly. He said he remained on his stomach going down the stairs and then lay face down under the plane while, he said, the Egyptians were "shooting indiscriminately" at passengers who fled the plane.

"If I had raised my head," he said in a hospital beside interview, "I think I would have been killed."

A witness of the rescue attempt who watched it from the control tower, where Prime Minister Carmelo Mifsud Bonnici and his Cabinet had gathered during the 24-hour crisis, recalls hearing the initial explosion, several lesser explosions, then the firing that went on for "more than a minute."

"I thought, 'My God!,' " he recalled, " 'Why are they shooting so much when there are only two hijackers in there?' "

Maltese officials have consistently spoken of there being four to five hijackers. But surviving passengers, including those shot at by the hijackers' leader in a series of staged "executions," reported only three hijackers, one of whom was killed by an airline security guard before the plane landed here Saturday night.

The hijackers forced two other persons on the plane -- apparently a steward and another a passenger -- to help them collect the passports of the passengers and later to tie the hands of those Israelis and Americans selected to be shot. It was the assistance of these two persons, diplomats here suggested, that gave rise to the reports that there were four or five hijackers.

According to accounts being pieced together here, one hijacker was standing at the rear of the plane when the Egyptian bomb went off and apparently was killed. The other hijacker, who was in the cockpit holding a gun to the head of pilot Galal, apparently threw one of his grenades after the big explosion, then, in a fight with Galal, was seriously wounded with a fire ax.

After numerous passengers were taken to look at the suspected hijacker in the intensive care ward of St. Luke's Hospital Monday, he was "positively identified" as the leader, Maltese government officials said.

Maltese government spokesman Paul Mifsud confirmed today that the Egyptian government has made a formal extradition request for the wounded suspect. He was identified as a Tunisian who boarded the plane under the name of Omar Marzouki. Sources said he remained too ill, after an operation to repair a damaged lung, to be interrogated.

While not ruling out the possibility that the court might decide in favor of extradition, despite the fact that Malta and Egypt have no extradition treaty, Mifsud said: "If there is enough evidence to bring him to justice for crimes committed on Maltese soil he will be tried in Malta."

Egyptian sources said today that Marzouki is a Tunisian who boarded a flight from Tripoli, Libya, to Athens, and who waited the morning of the hijacking to board the Egyptair flight to Cairo. Mubarak has said Libya is behind the hijacking.

Libyan leader Muammar Qaddafi denied any role in the attack. Interviewed on the MacNeil-Lehrer Newshour, he said, "I am sure there is no relationship between Libya and this . . . hijacking."

The Tunisian Embassy in Washington denied that anyone namedMazourki held a Tunisian passport and noted that Tunisian passports had been stolen recently from embassies in European and Arab countries.

The Egyptian sources said Marzouki had asked Galal to fly to Tripoli after the hijacking, but the pilot refused.