The sound of an explosion can be heard on the black box recorder of the downed Russian jet, according to reports in France. The France 2 TV channel quotes an investigator with access to the black box - but the country's BEA accident and investigation body said it could not confirm his claims.
If correct, the report supports UK intelligence that a bomb was smuggled into the hold of the Metrojet plane that crashed in Egypt last weekend, killing all 224 people on board.
It is claimed that US officials reported chatter between Islamic State leaders in Sinai and Syria about the Egypt plane, and discussions included boasts about taking down an airliner and how it was done.
"They were clearly celebrating," the US broadcaster NBC reported, citing US officials.
UK spies found evidence of a major plot in intercepts picked up during a review of the disaster, Sky News understands.
Sky's Foreign Affairs Editor Sam Kiley said: "Following the downing of the aircraft, British intelligence went back over existing material and began to see some kind of signal that indicated a bomb had been placed on this aircraft."
The discovery has created a diplomatic row between the UK and Russia, who, having previously played down Islamic State claims of responsibility, want to see the intelligence.
Kiley said: "The interesting thing is that the intelligence was missed in the first place, which will anger the Russians in particular.
"The Russians and Egyptians want the British to share this intelligence with them.
"The British are resisting that very strongly - quite often they've said they'll share the conclusions but not the raw material because access to the raw material will reveal their capabilities."
Western intelligence sources who spoke to Reuters said the evidence was not categorical and there was no hard forensic or scientific evidence to support the bomb theory.
As the investigation into the cause of the disaster continues, flights from Sharm to the UK have resumed in the face of heightened security.
The US has tightened security on planes heading from Egypt, while Russia has followed the UK in suspending flights - but Vladimir Putin insists this is not because he is convinced of the bomb theory.
It has also been announced Britain will set up a small military operations team in Egypt to monitor extremism in the region.