Two weeks after coordinated bombings at several Red Sea resorts in Egypt, Israeli and Egyptian investigators have yet to assemble a clear picture of how the attacks occurred or identify the people or group behind them, according to officials who described a frustrating shortage of evidence, the same problem that plagued other major terrorism inquiries in the early stages.

The Oct. 7 attacks along the Sinai Peninsula's rugged east coast killed 34 people, many of them Israeli tourists in the midst of a long holiday weekend. In the past two weeks, investigators from Egypt and Israel have pored over evidence from three crime scenes. Egyptian officials have questioned dozens of tribesmen from the remote desert region, which provided the attackers with vulnerable targets and a seemingly traceless escape.

Drawing on fragments of evidence and traits the case appears to share with large attacks in Africa and Europe since May 2003, Egyptian and Israeli investigators say they believe the Sinai bombings were carried out by Egyptians who belong to a previously unknown cell inspired by the global ambitions of al Qaeda and guided by experienced foreign militants.

Those initial conclusions fit a pattern that emerged from investigations into bombings in Madrid, Istanbul and Casablanca, Morocco, but only after months of following leads that at various turns pointed to different organizations with vastly different motives. As in those cases, the first phase of the Sinai inquiry highlights how difficult investigating terrorism has become at a time when rising violence in the Middle East is moving scores of anonymous young men to take up arms against the United States and allied governments.

"This is an octopus with al Qaeda at its heart," Col. Zohar Alafi, deputy director of the Israeli military's intelligence research division, said last week during a hearing of the Israeli parliament's Foreign Affairs and Defense Committee. "It is composed of independent cells whose common denominator is hatred of Jews and Christians and the desire to topple 'heretic regimes' that cooperate with the United States and Israel."

Investigators from Egypt and Israel, whose inquiries are largely independent of one another, agree that the nearly simultaneous attacks on the Taba Hilton and a pair of camp-style resorts farther south along the lightly guarded Sinai Peninsula had likely been planned for more than a year. The bombings killed 11 Israelis, eight Egyptians, one Russian, two Italians and 12 people whose nationalities are unconfirmed, according to the Associated Press.

In recent days, Egyptian officials, speaking anonymously to national media, have said the explosives employed were the same kind used in quarries in the Sinai -- a lead Israeli investigators said they were also pursuing.

Egyptian officials moved quickly in the days after the blast to round up dozens of Bedouin tribesmen, semi-nomadic herders who know the barren Sinai intimately. One of those detained admitted that he had sold explosives to a visitor to the peninsula recently, according to Egyptian investigators, but said he did not know what they would be used for.

The Sinai is a lightly populated triangle of arid plains carved by narrow canyons, and it presented attackers with a susceptible target. About 4,000 Bedouins move around the peninsula within rough tribal boundaries. Many of them have become skilled smugglers, and many also handle explosives to quarry rock from the craggy hills.

Much of the rest of the population is migrants from other parts of Egypt drawn to what is known as the Red Sea Riviera for work in the tourism trade. Those demographics make the people of the Sinai hard to know or track, Egyptian authorities say.

Moreover, several political analysts said, the 1978 Camp David accord that returned the Sinai to Egypt after 11 years of Israeli occupation established a 24-mile buffer zone along the frontier. The agreement left the zone guarded only by a U.N. force and an Egyptian "civil police force equipped with light weapons."

"This is a very big part of the problem," said Montasser Zayat, a Muslim lawyer who once belonged to the anti-government Islamic Group and now represents defendants accused of terrorist-related crimes. "There is much more freedom of movement there."

Cars and people entering the small community of Taba from central Egypt or the southern Sinai are required to stop at a checkpoint controlled by Egyptian security forces, but cars are frequently waved through without inspection. The Taba Hilton had no barriers.

"This was not a problematic border at all," said Gil Kleiman, spokesman for the Israeli national police. "The Israelis, unfortunately, always treated Taba like a suburb of Eilat," the Israeli port just across the border.

After initially believing that car bombs in Taba and Ras Shytan were set off by suicide attackers, Egyptian officials have concluded that the bombs were likely triggered by timers. The technique suggests a higher degree of sophistication than a suicide mission and deprives investigators of a key piece of evidence -- the bomber.

Egyptian authorities say they are looking for four attackers, including one who abandoned his car just outside the walls of one camp in Ras Shytan after being discovered by a security guard. The car exploded harmlessly. One Egyptian investigator told the weekly magazine Al Mussawar this week that authorities are working on "specific leads" and suggested that arrests are imminent.

Since the 1997 attack in Luxor that killed 58 tourists, the government of President Hosni Mubarak has made peace with several anti-government extremist groups, offering prisoner amnesties in exchange for renunciations of violence. At the same time, domestic intelligence services have ratcheted up monitoring of groups -- such as the al Qaeda-affiliated al Jihad -- that remain the government's committed enemies.

"As we've followed them, there have been many indicators that they are suffering financially," said Fouad Allam, a retired official of the Interior Ministry who now serves as a consultant there. "The explosions in Taba were well financed, so it doesn't make much sense that it was one of these Egyptian groups."

Although Palestinian groups were initially mentioned as possible suspects, investigators and political analysts in both countries now say such organizations would probably not have risked their good relations with Egypt to carry out such an attack. Rather, investigators and political analysts say, the bombers were likely stirred to act by the violence they have witnessed in the Palestinian territories and by the U.S. involvement in Iraq.

Egyptian officials appear to be leaning toward what one investigator characterized as "local centers" of terrorism -- domestic groups, perhaps previously unknown, whose members relied on Bedouins for logistical help. Israeli analysts agree, in broad terms, with those conclusions.

"We can see the same patterns over and over," said Boaz Ganor, executive director of the International Policy Institute for Counter-Terrorism, in the Tel Aviv suburb of Herzliya. Ganor, whose institute has a close relationship with the Israeli intelligence and military communities, cited previous militant attacks in Istanbul, Madrid and Kenya.

"The planning, the recruitment, the processing of the intelligence was done by al Qaeda, but the people who actually are responsible for the attack in the field in many cases were local Islamic radical activists," he said. "This is the same pattern right here again."

Zayat, the lawyer and former member of the Islamic Group, said the attacks bear the hallmarks of an organization with a "jihadist ideology" -- a group that, like al Qaeda, subscribes to the ambition of global holy war rather than the regional goals of Palestinian groups.

"These are people influenced by what is happening in Palestine and Iraq, and inspired by the tapes of bin Laden" and his Egyptian lieutenant, Ayman Zawahiri, Zayat said. "But I think saying this is carried out by al Qaeda from outside Egypt is a very weak scenario."

Moore reported from Jerusalem. Wilson reported from Cairo and Amman.

Israeli and Egyptian search teams work in the rubble of the Taba Hilton after the hotel, which is close to the Israeli border, was hit by an attack on Oct. 7.