REUTERS/Stringer Egypt's Prime Minister Sherif Ismail (R) listens to rescue workers as he looks at the remains of a Russian airliner after it crashed in central Sinai near El Arish city, north Egypt, October 31, 2015.
The jet"broke up in the air", a Russian aviation official said on Sunday, adding that it was too early to talk about conclusions from the crash, Russian news agencies reported.
Viktor Sorochenko, an official with the Intergovernmental Aviation Committee, made the comments after inspecting the crash site on Egypt's Sinai peninsula.
In-flight break-ups are exceedingly rare for modern airliners such as the Metrojet Airbus A321 involved in the crash.
According to media reports, the 18-year old jet disappeared from radar while flying at 31,000 ft. 20 minutes after taking off from the Egyptian resort town of Sharm el-Sheikh.
The most publicized recent break up of an airliner mid-flight is the crash of Malaysia Airlines MH17 which was shot down by a surface-to-air missile over Ukraine in July of 2014.
There are also less nefarious reasons that could cause an airliner to break apart. In 2002, China Airlines Flight 611, broke apart over the Taiwan Strait at 35,000 ft., killing 225 people. The cause of the crash was eventually attributed to structural failure resulting from improper repairs made to the plane after its tail was damaged during a landing 20-years earlier.
According to the Air Safety Network, records indicate the Airbus A321 involved in Saturday's crash also suffered a tail strike in November 2001 while landing in Cairo. However, it is unclear if the incident has any causal relationship to the Sinai crash.
At this point in the investigation, it is too early to make any conclusion as to what may have cause the incident. However, investigators will have much to work with once they extract the information from the aircraft's fiight data recorder and cockpit voice recorder.