Police have also searched the airline’s offices.
The wife of the co-pilot says her husband complained of technical issues with the aircraft.
Egypt has dismissed an ISIL claim that it downed the plane.
Air France-KLM, Emirates and Lufthansa have stopped flying over the Sinai Peninsula until the cause of the crash is known.
The plane came down 23 minutes into a flight from the Red Sea resort of Sharm el-Sheikh to St Petersburg.
In Cairo the bodies of the victims arrived at a morgue before being returned to Russia.
Our correspondent in Cairo Mohammed Shaikhibrahim says: “What has arisen from the information investigators have is the hypothesis that the crash was caused by a a technical failure.
Another strand is the plane was attacked in the light of increased militant activity in Sinai.
The answers will lie in the black box flight recorders.”
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