A Russian aviation official says the Russian airliner that crashed in the Sinai Peninsula broke apart in midair. The first remains of the victims have been flown to St Petersburg.
Russia's emergency ministry flew recovered remains to Russia's second largest city for identification on Monday as Russian investigators at the crash site in Egypt gathered evidence.
Russian officials said on board were remains of 144 victims among the 224 occupants of Saturday's ill-fated plane.
Most of those killed were vacationers from Saint Petersburg and its surrounding region.
On Sunday, the chief of Russia's Interstate Aviation Committee, Viktor Sorochenko, who is leading a panel of experts probing the crash in Egypt, had said the Russian Airbus A321 "broke up in the air."
"The disintegration happened in the air and the fragments are strewn over a large area," Sorochenko said after inspecting wreckage. He also said it was "too early to draw conclusions" about what caused the crash.
Prior 'technical problems'
An anonymous source at Sharm el-Sheikh airport told DW on Sunday that the plane had been reported for "technical problems" two months ago and had been grounded.
The plane, operated by Russian airline Kogalymavia, was en route to St. Petersburg from the Red Sea resort of Sharm el-Sheikh when it lost contact with air traffic control and crashed into a mountainous part of the restive Sinai region early Saturday.
Authorities announced Sunday they would widen the search area to 15 kilometers (9.3 miles), given that debris was scattered.
Russia has sent more than 100 emergency workers to Sinai to assist with search efforts. Air accident investigators from France - Airbus's home country - are also to travel to Egypt along with investigators from accident investigation agencies in Germany and Russia. Experts were to begin examining the flight's black boxes later on Sunday.
Questions over cause
Just hours after the crash, a group affiliated with "Islamic State" (IS) in Sinai claimed responsibility, saying it had shot down the plane as revenge for "Russian airstrikes that killed hundreds of Muslims on Syrian land."
But authorities in both Russia and Egypt questioned the accuracy of the claim. Experts say the militants waging an Islamist insurgency in the Sinai don't have weapons capable of hitting a plane flying at 9,000 meters (30,000 feet). They haven't ruled out that a bomb could have been on board, but say it's more likely the crash happened due to technical or human error.
Egyptian President Abdel-Fattah el-Sissi urged people to wait for the outcome of the investigation before jumping to conclusions.
"Leave it to specialists to determine the cause of the plane crash because it is a subject of an extensive and complicated technical study," state news agency MENA quoted El-Sissi as saying.
Meanwhile, Lufthansa, Air France and Emirates said they would avoid flying over the Sinai Peninsula until the cause of the crash became clear. Germany's transport ministry also warned the country's airlines not to use the same flight path over the northern and southeastern parts of the peninsula.
A woman lights a candle during a requiem in memory of the victims in St. Petersburg's Kazan Cathedral
Day of mourning
Sunday was declared a day of mourning in Russia, where the national flag could be seen flying at half mast at the State Duma and other official buildings. Hundreds of people laid flowers and toys at makeshift memorials at airports in St. Petersburg and the capital, Moscow.
Authorities set up a crisis center at a hotel near the St. Petersburg airport, where relatives of the victims were invited to provide DNA samples to help identify the dead.
Russia's emergency ministry said it would begin delivering the victims' bodies home later on Sunday. The government said it would pay compensation to the families and help organize funerals.
The crash victims included 214 Russian passengers, three Ukrainians and seven crew members.
nm/jm (Reuters, AFP, AP, dpa)