The remains of a Russian airliner
The remains of a Russian airliner are inspected by military investigators at the crash site at the al-Hasanah area in El Arish city, north Egypt Reuters

Investigators found elements "not related" to the aircraft at the crash site of Russian airliner Flight 9268, which crashed in Egypt's Sinai peninsula on Saturday (31 October), killing all 224 people on board.

"Experts have found elements not related to the aircraft structure in the area of the disaster," a source in Cairo close to the investigation told Itar Tass news agency. "They sent them for examination."

It comes as conflicting accounts emerged of what happened to the plane while it was en route from Sharm el Sheikh to St Petersburg, with airline officials suggesting it was brought down by an "external object", while US intelligence sources claim it was probably brought down by an internal explosion.

On Monday, November 2, an official from the Metrojet airline which owned the plane said that it could only have been brought down by "external factors". "We rule out a technical fault of the plane or a pilot error," Alexander Smirnov, deputy general director of Metrojet, told a news conference in Moscow.

However, Egyptian president Abdel Fattah al-Sisi dismissed as "propaganda" claims of responsibility for the crash from jihadist group Isis. "When there is propaganda that it crashed because of Isis (IS), this is one way to damage the stability and security of Egypt and the image of Egypt. Believe me, the situation in Sinai — especially in this limited area – is under our full control," he told the BBC.

US defence officials told NBC that a US infrared satellite detected a heat flash at the same time and in the same vicinity as the plane crash, and ruled out any possibility of it being hit by a surface-to-air missile attack. The official said evidence suggested there had been an explosion on the plane, which disintegrated in mid-air.

US director of national intelligence James Clapper earlier told a security conference in Washington DC that there was not yet any "direct evidence" of terrorist involvement in the crash.

Egyptian investigators are probing the cause of the crash with officials from Russia, Airbus and Ireland, where the plane was registered.