An investigation is under way after a Russian airliner crashed in Sinai, killing all 224 people on board.Egypt ' s prime minister said a technical fault was the most likely cause, dismissing claims from Islamic State militants that they were responsible. However, three airlines - Emirates, Air France and Lufthansa - have decided not to fly over the Sinai Peninsula until more information is available.Recommended:Russian plane crashes in EgyptThe plane ' s black boxes have been found and sent for analysis, officials said. The Kogalymavia Airbus A - 321 came down early on Saturday, shortly after leaving the resort of Sharm el - Sheikh for the Russian city of St Petersburg. Egypt ' s civil aviation minister Hossam Kamal said there had been no sign of any problems on board the flight, contradicting earlier reports that the pilot had asked to make an emergency landing.Recommended:No survivors on Russian crashed plane An Egyptian official had previously said that before the plane lost contact with air traffic controllers, the pilot had said the aircraft was experiencing technical problems and he intended to try to land at the nearest airport.