Russia has returned 11,000 of its tourists from Egypt in the last 24 hours in response to the plane crash in the Sinai Peninsula a week ago, RIA news agency said on Sunday, but tens of thousands more are waiting for flights home.

The chief Egyptian investigator into the crash of the Russian airliner on 31 October which killed all 224 people on board said his team was considering all scenarios for the cause of the tragedy after reporting a noise registered in the last seconds of the flight recording. Western countries suspect a bomb was planted by militants.

A leading airline predicted the disaster will lead to stringent aviation security worldwide.

Thousands of mostly Russian and British tourists are stranded at Sharm El-Sheikh airport, where the Airbus A321 took off for St Petersburg before crashing 23 minutes into the flight.

Around 80,000 Russians were left in Egypt after the Kremlin grounded all flights to the country on Friday following the crash, due to security concerns.

A British official said on Saturday it could take 10 days for all British tourists to be flown home.

The crash occurred when the auto-pilot was engaged. Debris was scattered over a 13-km (8-mile) area "which is consistent with an in-flight break-up", said Ayman Al-Muqaddam, head of the investigation committee.

Emirates Airlines President Tim Clark said he expected the crash would result in demands for stringent aviation security worldwide. Speaking at the Dubai Airshow, Clark said he had ordered a security review, but was not suspending any flights as a result of the disaster. Emirates does not operate regular flights to Sharm al-Sheikh.

Islamic State group militants fighting security forces in Egypt's Sinai Peninsula have said they brought down the aircraft as revenge for Russian air strikes against Islamist fighters in Syria, where the group controls large areas in the east and north of the country. They said they would eventually tell the world how they carried out the attack.

If the group was responsible, it would have carried out one of the highest profile killings since al Qaeda flew passenger planes into New York's World Trade Center in September 2001.

On Saturday, security officials said Egypt is checking video footage at Sharm El-Sheikh airport for any suspicious activity linked to the crash, the clearest sign yet that Cairo suspects it could have been targeted by militants.