The U.S. and U.K. claimed Wednesday that a bomb might have brought down a Russian airliner, which crashed in Egypt, as the Islamic State of Iraq and al-Sham (ISIS) group had claimed earlier.The U.K. and Ireland suspended flights to and from the Egyptian Red Sea resort area of Sharm el-Sheikh, where the plane took off on Saturday before crashing minutes later, killing all 224 people on board. "A bomb exploding is a highly possible scenario," a U.S. official told AFP. "It would be something that ISIS would want to do," he added.British Prime Minister David Cameron's office said that "as more information has come to light, we have become concerned that the plane may well have been brought down by an explosive device." The move comes as Egyptian President Abdel-Fattah al-Sissi was set to hold talks with Cameron in London yesterday, during his first visit to Britain since he led the army's overthrow of the country's first democratically elected president, Mohamed Morsi.In Russia, authorities are expected to bury the first victim of the crash – the country's deadliest air disaster ever. Moscow and Cairo both dismissed ISIS's initial claim that it brought down the Airbus A-321 in Egypt's restive Sinai Peninsula, but the extremists on Wednesday again insisted they were responsible and promised to reveal how.Egyptian officials said investigators probing the plane's black boxes had extracted the data from one of them for analysis, but added the other had been damaged and required a lot of work. In a new statement Wednesday, ISIS again insisted it had brought down the plane – and challenged skeptics to prove otherwise. "Prove that we didn't bring it down, and how it came down. We will detail how it came down at the time of our choosing," the group said in an audio statement posted online.The ISIS affiliate in Egypt is waging a bloody insurgency in the north of the Sinai Peninsula and hundreds of policemen and soldiers have died as a result. On Wednesday, the affiliate claimed responsibility for a suicide car bombing on a police social club in El-Arish, which the official MENA news agency said killed four policemen. ISIS has deployed shoulder-fired anti-aircraft missiles in the past, but they are not known to possess weapons that could bring down an airliner at high altitude. Egypt has played down the possibility of a bomb attack and stressed the need to wait for the results of an international investigation, keen to preserve the country's economically vital tourism sector.Cameron's office said he and Sissi had agreed on the need for tighter security at Sharm el-Sheikh Airport, and British aviation experts have been dispatched to the resort to assess security.Flight KGL9268 was flying at an altitude of 30,000 feet (9,144 meters) when it lost contact with authorities, 23 minutes after takeoff. A U.S. military satellite picked up a heat flash at the time of the crash that could point to a catastrophic event during the flight, U.S. media reported. Russian President Vladimir Putin has described the crash as a "huge tragedy." Relatives of the victims have begun identifying the bodies after two planes delivered the remains of many to Saint Petersburg. In the city center, about 300 people attended a vigil for the dead on Wednesday.If confirmed, it would be the first time the militant group, which controls vast tracts of Syria and Iraq, has bombed a passenger plane. After the crash, flights have been halted and concerns over civil aviation have risen. Several airlines, including Lufthansa and Air France, assessed the risks and stopped flying over the Sinai. Britain also halted flights to and from Egypt's Sharm el-Sheikh airport on Wednesday. Budget airline easyJet said its flights to and from Sharm el-Sheikh were cancelled yesterday due to the government's advice and that its future schedule would be reviewed. All passengers booked to travel to the airport in the next two weeks can request a refund or change their flights, the airline said, while passengers delayed in Egypt will be given hotel rooms.The suspension of flights is a further blow to Egypt's troubled tourism industry, which has suffered from the unrest that followed the 2011 Arab Spring. The one bright spot for Egypt has been tourism at the Red Sea resorts. British Foreign Secretary Philip Hammond said an estimated 20,000 Britons currently in the Red Sea resort of Sharm el-Sheikh will be assisted to leave. "There is a significant possibility that the crash was caused by an explosive device on board the aircraft," he said after an emergency cabinet meeting.Meanwhile, another plane crashed shortly after taking off from South Sudan's capital Juda on Wednesday and killed at least 36 people.