SHARM EL-SHEIKH, Egypt -- A noise was heard in the last second of the cockpit voice recording from the Russian plane that crashed last week in Egypt's Sinai, killing all 224 people onboard, the head of the investigation team said Saturday.
Ayman el-Muqadem told a news conference in Cairo that an analysis of the noise was underway to identify its nature. He said the way the debris was scattered over a wide area indicated the Airbus A321-200 broke up mid-air, but initial observations don't shed light on what caused it.
Sources told CBS News on Friday the sound of an explosion can be heard on the cockpit voice recorder although that still does not conclusively point to a bomb, CBS News homeland security correspondent Jeff Pegues reports.
"All scenarios are being considered ... it could be lithium batteries in the luggage of one of the passengers, it could be an explosion in the fuel tank," said El-Muqadem, who is Egyptian and leading the investigation committee. It includes members from Russia, France, Germany and Ireland, where the plane was registered.
U.S. and British officials have cited intelligence reports as indicating that the flight from the Sinai resort town of Sharm el-Sheikh to St. Petersburg was brought down on Oct. 31 by a bomb on board.
Investigators found debris scattered across a 13-kilometer stretch of desert, but some pieces of wreckage were still missing, el-Muqadem said. Recovered wreckage will be taken to Cairo for analysis.
Also Saturday, Egypt's foreign minister complained that Western governments had not sufficiently helped Egypt in its war on terrorism and had not shared relevant intelligence with Cairo.
Sameh Shoukry, speaking at a press conference, said that "European countries did not give us the cooperation we are hoping for."
Egypt's past calls for assistance and coordination on terrorism issues from "the countries that are now facing the danger" had not been dealt with seriously, he said.
Shoukry also complained that Western nations that have suspended flights to Sharm el-Sheikh did not share with Cairo the relevant intelligence upon which they based their decisions. Egypt "expected that the information available would be communicated to us instead of being broadcast" in the media, he said.
The foreign minister's comments came as Egypt launched an investigation into the staff and ground crew at the Sharm el-Sheikh airport, according to Egyptian airport and security officials.
The officials told The Associated Press on Saturday that authorities were questioning airport staff and ground crew who worked on the Russian flight and had placed some employees under surveillance. The officials all spoke to the AP on condition of anonymity because they were not authorized to speak to the media.
Reports quoting unnamed British officials said security footage from the airport showed poor checks on staff entering the airport, CBS News correspondent Allen Pizzey reports. The evidence of lax security, coupled with British intelligence reporting, are believed to be what sparked Britain's ban of flights to Sharm el-Sheikh earlier in the week.
The crash one week ago dealt another blow to Egypt's battered tourism sector, which is yet to fully recover from years of political turmoil. Russians comprise nearly a third of all tourists who visited Egypt in the past year.
Extremists with the Islamic State of Iraq and Syria, or ISIS, have claimed that they brought down the Russian Metrojet flight, with mostly Russian tourists onboard, though they did not offer any proof.
Egyptian authorities have been trying to whip up support for a war on terror after the military overthrow of Islamist President Mohammed Morsi in 2013. A crackdown on Islamists and a series of militant attacks on security buildings and checkpoints, mainly in the restive Sinai Peninsula, have followed Morsi's ouster - with a Sinai-based affiliate of ISIS claiming responsibility for some of the most devastating attacks.
On Friday evening, Russia suspended all flights to Egypt. Ireland has also suspended flights to the Red Sea resort, while at least a half-dozen Western European governments told their citizens not to travel there. Empty charter planes have been flying to Sharm el-Sheikh to bring home stranded Russian and British tourists. But these flights banned passengers from checking in luggage - reflecting an apparent concern about security and luggage-screening procedures at the airport.
Tourism chief Oleg Safonov said, according to Russian news agencies, that a revised count showed 80,000 Russians currently in Egypt - 79,000 of them in the resort areas of Hurgada and Sharm el-Sheikh.
Maya Lomidze, acting director of the Russian Association of Tour Operators, said 46 empty Russian planes were expected to be sent to Egypt on Saturday to bring tourists home and another 47 flights were planned for Sunday. The Russian Emergencies Ministry also said it would send planes to Egypt to bring back the checked baggage of Russian tourists who were forced to leave their suitcases behind.
Egypt's military was registering departing passengers for flights out of the country, Russian Deputy Prime Minister Arkady Dvorkovich said. Russia's federal aviation agency Rosaviatsiya said 13 flights left Egypt on Saturday bound for Russia - nine from Hurghada and four from Sharm el-Sheikh.
Ivan Zaitsev, who works in the printing industry, and his wife and young son were in a long, snaking line of Russian and Kazakh tourists trying to leave Sharm el-Sheikh. He said their travel agent told them the Moscow-bound flight would leave Saturday but that it hadn't appeared on the monitor yet.
"I think if the government decided something like this they have their reasons ... we're really hoping to fly back safely. This is the main issue now," Zaitsev said.
More than 100 Russian passengers were left behind in Sharm el-Sheikh early Saturday because they didn't want to leave their check-in luggage in Egypt.
The news of the canceled flights didn't reach all would-be Russian vacationers. At Pulkovo Airport in St. Petersburg, some travelers arrived on Saturday unaware they wouldn't be able to fly. Some were disappointed, but appeared to be trying to take the news in stride.
"If there is a reason to cancel, then it's better not to fly," tourist Vyacheslav Kuznetsov said.
Meanwhile, British media on Saturday reported more troubling news for the Egyptian tourism industry, saying a plane carrying British tourists narrowly missed being hit by an Egyptian missile in August. The British government and Thomson Airways confirmed the incident.
The Guardian and other British media said a rocket came within 1,000 feet of a Thomson jet bound for Sharm el-Sheikh with 189 passengers onboard on Aug. 23.
The British Department for Transport said its investigation concluded it was not a "targeted attack" and likely connected to routine Egyptian military exercises in the area at the time. Thomson said there was "no cause for concern" for further flights.