But they say they have yet to reach a formal conclusion.
Britain earlier suspended flights to and from the resort of Sharm el-Sheikh, from where the flight had departed, the BBC reports.
Egypt has dismissed claims by militants linked to Islamic State (IS) that they brought down the plane.
Separately on Wednesday, Egyptian officials said the cockpit voice recorder of the Metrojet Airbus 321 was badly damaged in the crash.
However, they managed to extract information from the flight data recorder which is ready to be analysed by investigators, Egypt’s Civil Aviation Minister, Mohamed Hossam Kamal, said.
The plane, bound for St Petersburg, crashed in Egypt’s Sinai desert just 23 minutes after take-off from Sharm el-Sheikh on Saturday.
Most of those on board the plane, which was operated by Russian airline Kogalymavia, were Russian.