British prime minister David Cameron halted flights to and from Sharm al-Sheikh on Wednesday after intelligence shown to him indicated that it was likely that the Airbus A321 heading towards St Petersburg was brought down by a bomb.
Britain says there was a “credible threat” but has refused to comment further on the intelligence involved.
Western intelligence sources said some of the assessment about the bomb came from intercepted communications both from suspected militants and from one or more governments involved in the investigation.
The sources said the evidence was not categorical and there is still no hard forensic or scientific evidence to support the theory.
“We still cannot be categorical but there is a distinct and credible possibility that there was a bomb,” one source said.
Two sources said the bomb may have been hidden in luggage in the hold of the plane.
A Sinai-based group affiliated with Islamic Statehas claimed responsibility for the crash, which, if confirmed, would make it the jihadist organisation’s first attack on civil aviation.
“The theory of an explosive device, with local complicity, is being taken seriously. Nothing is proven yet, but it is a real possibility,” a European official said after being briefed by a Western intelligence agency.
“They believe that what Daesh [Islamic State] is saying has a good chance of being credible.”
A US government source said some of the “chatter” intercepted about the bomb included conflicting details about whether the bomb was placed on the plane.
Russia, which was initially critical of Britain’s assessment of what it has called a crash, yesterday suspended all flights to Egypt.
Russian president Vladimir Putin ordered the halt to flights after Alexander Bortnikov, the head of Russia’s FSB security service, recommended Russia suspend all passenger flights to Egypt until it knew exactly what caused the crash.
“Until we know the real reasons for what happened, I consider it expedient to stop Russian flights to Egypt,” said Bortnikov. “Above all, this concerns tourist routes.”
Meanwhile, eight flights yesterday left Sharm el-Sheikh bound for Britain with 1,400 stranded holidaymakers on board. The first passengers arrived back in the UK to Gatwick at 4.25pm followed by seven other aircraft throughout the day.
Around 4,000 Brits were initially expected to be flown home but the other 21 scheduled flights were cancelled by the Egyptian authorities, with some planes forced to turn around in mid-air.