A U.S. official briefed on the matter says U.S. intelligence agencies have assembled preliminary evidence that a bomb brought down the Russian airliner.
The official says intercepted communications played a role in the tentative conclusion that the Islamic State group's Sinai affiliate planted an explosive device on the plane.
The official, who spoke on condition of anonymity, and others said there had been no formal judgment rendered by the CIA or other intelligence agencies, and that forensic evidence from the blast site, including the airplane's black box, were still being analyzed.
A Russian passenger plane carrying more than 220 people crashed more than 20 minutes after takeoff from a Red Sea resort popular with Russian tourists, Egypt's Ministry of Civil Aviation said.
Britain said Wednesday it has information suggesting the Russian jet that crashed in the Egyptian desert may have been brought down by a bomb and it was suspending flights to and from the Sinai Peninsula as a precaution.
At the same time, Russian and Egyptian investigators said the cockpit voice recorder of the Metrojet Airbus 321-200 had suffered substantial damage in the weekend crash that killed 224 people. Information from the flight data recorder has been successfully copied and handed over to investigators, the Russians added.
Prime Minister David Cameron's office said British aviation experts were headed to the Red Sea resort of Sharm el-Sheikh, where the flight originated, to assess security before British flights there would be allowed to resume.
A ministry statement said Egyptian military search and rescue teams found the wreckage of the passenger jet in the remote mountainous Hassana area 44 miles south of the city of el-Arish, an area in northern Sinai where Egyptian security forces are fighting a burgeoning Islamic militant insurgency led by a local affiliate of the extremist Islamic State group.
The group claimed responsibility for downing the jet, Sky News reported.
The Wilayat Sinai group claimed on Twitter Saturday that "the fighters of the Islamic State were able to down a Russian plane over Sinai province that was carrying over 220 Russian crusaders. They were all killed, thanks be to God." The statement was also posted on a website that serves as an unofficial news agency for the terror group, Sky News reported, adding that the claim has not been verified and it is unclear whether Sinai militants have the capability to attack a plane flying at a high altitude.
The plane, an Airbus A-321 operated by Russian airline Kogalymavia and branded as Metrojet, according to the aviation ministry, took off from Sharm el-Sheikh shortly before 6 a.m. for St. Petersburg in Russia. It disappeared from radar screens 23 minutes after takeoff.
The Egyptian officials said the aircraft was cruising at 36,000 feet when contact with air traffic controllers was lost. Flight-tracking service FlightRadar24 said the plane was losing altitude at about 6,000 feet per minute before the signal was lost, Reuters reported.
Ayman al-Muqadem, an Egyptian official with the government's Aviation Incidents Committee, said the plane’s pilot, before losing contact, had radioed that the aircraft was experiencing technical problems and that he intended to try and land at the nearest airport. The aircraft crashed at a site near the el-Arish airport, he said.
Earlier, al-Muqadem told local media that the plane had briefly lost contact but was safely in Turkish airspace.
Adel Mahgoub, chairman of the state company that runs Egypt's civilian airports, said except for three Ukrainian passengers all on board were Russian citizens.
An Egyptian cabinet statement said the 217 passengers included 138 women, 62 men and 17 children.
Airbus said the aircraft was 18 years old and had been operated by Metrojet since 2012, Reuters reported. The plane had accumulated around 56,000 flight hours in nearly 21,000 flights.
Russian media said the airliner was a charter flight under contract with the Brisco tour company in St. Petersburg.
Separately, Russia's top investigative body opened its own investigation into the crash.
Militants in northern Sinai have not to date shot down commercial airliners or fighter-jets. There have been persistent media reports that they have acquired Russian shoulder-fired, anti-aircraft missiles. But these types of missiles can only be effective against low-flying aircraft or helicopters. In January 2014, Sinai-based militants claimed to have shot down a military helicopter; Egyptian officials at the time acknowledged the helicopter had crashed, but gave no reason.
Russian television showed scenes of relatives and friends gathering at St. Petersburg's Pulkovo airport, awaiting word on the fate of their loved ones. Russian President Vladimir Putin declared Nov. 1 a national day of mourning, according to a statement posted on the Kremlin's website.
Two of the passengers on the Metrojet flight, Elena Rodina and Alexqander Krotov, were newlyweds, a friend of the couple told the Associated Press at a hotel near the airport. They were both 33.
Yulia Zaitseva said Rodina “really wanted to go to Egypt, though I told her ‘why the hell do you want to go to Egypt?’”
“We were friends for 20 years,” she said. “She was a very good friend who was ready to give everything to other people. To lose such a friend is like having your hand cut off.”
She said Rodina's parents feel “like their lives are over.”
Roughly three million Russian tourists, or nearly a third of all visitors in 2014, come to Egypt every year, mostly to Red Sea resorts in Sinai or in mainland Egypt.
“It is too premature to detect the impact this will have on tourism. We need to know what happened first,” Tourism Ministry spokeswoman Rasha Azazi told the Associated Press.
The Associated Press contributed to this report