UK investigators looking at what caused a Russian airliner to crash in Egypt believe a bomb was put in the hold prior to take-off, the BBC has learned.
It had received intelligence based on intercepted communications between militants in the Sinai Peninsula.
However, both Egypt and Russia have said it is too early to draw conclusions.
The Metrojet Airbus A321 was flying from Sharm el-Sheikh to St Petersburg when it came down in Sinai on Saturday, killing all 224 people on board. Most of the victims were Russian.
Thousands of holidaymakers, 19,000 from the UK, remain stranded in Sharm el-Sheikh.
Many Britons were due to return on Friday but one of the main airlines operating from the resort, Easyjet, says its plans have been sharply curtailed by the Egyptian authorities, with only two of its 10 flights leaving.
Egyptian Aviation Minister Hossam Kamal denied banning any flights, but said there was an issue of "capacity" at the airport, with extra security and more planes than usual.
Anger in Moscow and Cairo: Jonathan Marcus, BBC diplomatic correspondentThe speed with which the British government pointed to terrorism as the possible cause of the downing of the Russian Airbus over the Sinai Peninsula has not gone down well in either Cairo or Moscow.
For the Egyptians the stakes are obvious: Sharm el-Sheikh and the wider tourism industry are crucial elements of its economy. This episode has punctured the long-held Egyptian narrative that Sharm el-Sheikh is insulated from the wider chaos in the Sinai.
For the Russians, an attack linked to so-called IS is also problematic. IS is the declared target of its air operations in Syria, but in reality Russian warplanes have largely been striking other rebel groups.
IS may now find itself in Russia's sights. But if IS did bring down the airliner, this could exacerbate concerns amongst Russian public opinion that their country's engagement in Syria is provoking some unpleasant blow-back.