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.
The UK government suspended all flights to and from the Egyptian resort of Sharm el-Sheikh two days ago.
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.
Britons stranded in Sharm el-Sheikh are due to begin returning on Friday, but will only be allowed to bring hand luggage.
However, one of the main airlines operating from the resort, Easyjet, has now said "rescue plans" have been "suspended by the Egyptian authorities".
A statement on its website says "discussions are currently ongoing at the highest political level to resolve this situation".
French-Dutch airline KLM is also restricting passengers flying from Cairo to hand luggage only.
BBC security correspondent Frank Gardner says that although British officials have not ruled out the possibility of a technical fault bringing the plane down, they think that is increasingly unlikely.
New intelligence was received on Wednesday and the UK government's Joint Terrorism Analysis Centre has spent the past few days assessing what caused the plane to come down.
Security service investigators suspect someone with access to the aircraft's baggage compartment inserted an explosive device inside or on top of the luggage just before the plane took off, our correspondent adds.
Sinai-based militants linked to the Islamic State (IS) group said they destroyed the plane, but did not say how. IS has called for a war against both Russia and the US over their air strikes in Syria.