Investigators analysing black boxes recovered from the Russian airliner that crashed in Egypt revealed last night that they had heard what appeared to be a bomb explosion.

A source quoted by media in France said that a “very sudden explosive decompression” could be heard 24 minutes into the flight, with everything appearing to be normal beforehand. The investigator ruled out engine failure. The revelation adds to evidence that an Islamist attack was behind the disaster.

A total of 224 people were killed when Russian Metrojet flight 9268 crashed in the Sinai desert on Saturday. Evidence from the plane’s black box “strongly favours” the theory that there was a bomb on board, a source close to the case said.

British and US spies intercepted chatter between Isis militants suggesting that a bomb had been placed in the luggage hold of the aircraft. Britain has not said who it believes is responsible but suspicions have fallen on Sinai Province, Islamic State’s Egyptian affiliate.

Amid growing alarm at the probability that a deliberate act had caused the crash, Russia cancelled flights to Egypt and ordered the evacuation of 50,000 holidaymakers. The US Department of Homeland Security announced new security measures, including tighter screening of items before they are brought on board aircraft.

Stranded holidaymakers from Ireland are still trying to get home from Egypt as Sharm el-Sheikh airport struggles to cope with chaotic flight schedules. About 179 Irish people are thought to be in the area, but the Department of Foreign Affairs said that the figure could be higher as some may not have registered with its consular division in Egypt.

Neither Aer Lingus or Ryanair fly directly to Sharm el-Sheikh, but the Irish Aviation Authority had directed the airlines to avoid airspace over the Red Sea resort where the plane went down.

No scheduled flights operate out of Dublin to Cairo or other Egyptian destinations at this time of year and no Irish travel agents have package holidays in the area at the moment. However, many Irish tourists are thought to travel to Egypt via British airports.

David Cameron came under pressure this week for the decision to ground British planes to and from the area. Soha Gendi, the Egyptian ambassador to Ireland, criticised the decision to suspend flights before investigations into the crash had finished.

“A decision of this importance should not be built on assumptions, but should wait until investigations are concluded, especially as the Irish team of experts participating in investigations are still there, alongside experts from Egypt, Russia, Germany and France,” Mr Gendi said.

Last night 1,500 travellers on eight flights had managed to leave the airport, with about 18,000 tourists remaining. A total of 21 scheduled flights had failed to take off. Egyptian authorities were accused of frustrating efforts to repatriate tourists from Sharm el-Sheikh after restricting the number of flights allowed to land.

Tourists who managed to get on a flight were instructed to only bring hand luggage, and the airport struggled to cope with the 120 tonnes of check-in baggage which was left behind. It will be flown back separately on secure flights arranged by the British government.

Britain’s ambassador to Cairo, John Casson, was heckled by angry holidaymakers at the airpoirt in Sharm el-Sheikh yesterday. Thomas Cook said that only one of four planned flights from the resort to the UK were able to operate yesterday, and said that customers were asked to return to their hotels last night.

Thomson Airways said that “a last-minute change in Egyptian government restrictions” meant it could only operate two flights back to Britain yesterday, and Monarch airlines also confirmed that it had been forced to cut five planned homebound flights down to two.

The suspension of British flights on Wednesday enraged Egyptian officials. It was announced as President Sisi of Egypt was in the air heading for his first official visit to Britain.

Russia’s decision to suspend flights is more far-reaching. Mr Putin acted after Alexander Bortnikov, the head of Russia’s federal security service, recommended that all passenger flights to Egypt be suspended until the cause of the crash was known. “The head of state agreed with these recommendations,” Dmitri Peskov, Mr Putin’s spokesman, said. About 45,000 Russians are on holiday in Sharm el-Sheikh alone, a third of all tourists in the resort.

Samples from the wreckage of Metrojet Flight 9286 have been taken to Moscow to be examined for possible traces of explosives. Sources at the Egyptian Civil Aviation Authority said that no extra security measures were being applied beyond the ban on hold luggage because the airport was “over capacity”. Egyptian special forces, however, were deployed to the tarmac.

Jeh Johnson, the United States homeland security secretary, said there would be increased security screenings of flights from some Middle East airports as a precaution.

A specialist team of British security experts had been sent to assess the security of Sharm el-Sheikh’s airport. A team of officials from the Irish Aviation Authority and the Department of Transport also travelled to Egypt on Monday to help with the investigation. The aircraft was registered in Ireland through a leasing company.