Officials say they have recovered the bodies of more than 120 passengers from the wreckage of a Russian plane that crashed on Egypt's Sinai Peninsula.
Egypt's Civil Aviation Ministry said there are no survivors among the 224 people who were aboard the plane.
Flight 9268 of the Russian airline Kogalymavia was flying from the Egyptian Red Sea resort of Sharm el-Sheikh to St. Petersburg early on October 31 when it crashed between the coastal city of Arish and the town of Hasna.
The Islamic State (IS) group affiliate in Egypt, Wilayat Sinai, claimed via Twitter that it had downed the plane, but Russia's transport minister swiftly rejected the statement.
Maksim Sokolov said the claim "can't be considered accurate," adding that authorities in Egypt "have no such information that would confirm such insinuations."
The site of the crash in the north-central part of the Sinai is described as mountainous and desolate.
Officials say the Airbus disappeared from radar about 23 minutes after taking off from the southern coast of the Sinai.
Egyptian officials say there were 217 passengers, including 17 children, and seven crew members on the plane.
Officials have said the overwhelming majority of the passengers and crew were Russian citizens. The Egyptian cabinet reported that there were three Ukrainians on board and the Belarusian Foreign Ministry said on its Twitter page that one passenger was a Belarusian citizen.
It is believed to be the deadliest aviation disaster in the history of Soviet and Russian aviation, surpassing a 1985 crash in Uzbekistan that left 200 people dead.
Egyptian Prime Minister Sherif Ismail, who flew to the crash scene, said that there did not appear to be any "unusual activity" behind the crash.
Ismail said it's impossible to determine the cause of the crash until the black boxes are examined.
Both black boxes from the plane have been found and sent for expert examinations, Egyptian officials said.
Russian aviation regulator Rosaviatsia said it didn't yet see any reason to blame the crash on a technical failure, an error by the crew, or external actions.
"Until there is reliable evidence about the circumstances of what happened, there is no sense in putting forward and discussing any versions," Rosaviatsia said in a statement on October 31.
WATCH: Passenger Bodies Recovered From Russian Plane Crash Site
The Sinai region where the plane crashed is the base of insurgents who support IS and who have killed hundreds of Egyptian soldiers and police in recent months, as well as having attacked some Western targets.
But Egyptian security sources said there was no indication that the Russian plane had been shot down or blown up.
Egyptian aviation officials had earlier said they suspected technical or mechanical reasons for the crash.
Two of Europe's largest airlines -- Lufthansa and Air France-KLM -- said on October 31 they would reroute flights to avoid flying over the Sinai Peninsula until the cause of the crash is determined.
In Moscow, Russian President Vladimir Putin declared November 1 a day of mourning for the victims of the crash.
A large delegation of Russian officials led by Emergency Situations Minister Vladimir Puchkov has been dispatched to Egypt.
Putin has also tasked Prime Minister Dmitry Medvedev with putting together a government commission to investigate the cause of the crash.
Medvedev wrote on Facebook that, "The circumstances of the accident will be thoroughly investigated" and "everyone affected by this tragedy will be provided with the necessary medical, psychological, and other aid."
He added that he was "deeply shocked by the crash" and that the loss of life "is a huge and irreparable loss."
Dozens of family members and friends were waiting at St. Petersburg's Pulkovo Airport for news about the fate of friends and loved ones.
They were put on buses and taken to a nearby hotel where counselors, psychologists, and other doctors were on hand to help them deal with the tragedy.
They also took DNA samples to help recover remains.
The mayor of the Russian city of Pskov, Ivan Tsetsersky, said that his deputy, Aleksandr Kopylov, was on the plane.
Russia's Investigative Committee has launched a criminal case against the airline Kogalymavia and raided the offices of the company in Moscow, seizing documents.
The RIA news agency reported that the Investigative Committee's case had been brought under an article regulating "violation of rules of flights and preparations for them."
Kogalymavia, which is also known as Metrojet and Kolavia, has been operating since 1993 and is based in the city of Kogalym, in Russia's Tyumen region.
The RIA and Interfax news agencies cited a spokeswoman for Kogalymavia as saying that there are no grounds to blame human error for the crash as the pilot had 12,000 hours of flying experience. She added that the plane had been fully serviced.
Roughly 3 million Russian tourists come to Egypt every year, mostly to the Red Sea resorts in the Sinai or on mainland Egypt.