LONDON — The British government on Wednesday suspended flights between Britain and the Egyptian resort of Sharm el Sheikh over concerns that a chartered Russian jetliner might have been brought down in the Sinai Peninsula by a bomb on board.
The announcement by Prime Minister David Cameron halting flights was the strongest action so far by any government official to suggest that the plane, which crashed within a half-hour of departing Sharm el Sheikh on Saturday, killing all 224 people on board, was brought down by an act of terrorism.
A European official briefed on the investigation said an initial inspection of the flight data recorder recovered from the plane indicated that the recording ceased abruptly, evidence that would support the theory of a midair explosion.
American military officials said Tuesday that satellite surveillance had detected a flash of light just as the jet broke apart, indicating it had blown up, because of a bomb, an accidental explosion of fuel or a catastrophic mechanical failure.
But American defense, intelligence and counterterrorism officials cautioned that it was premature to draw any firm conclusions. Though the United States is not part of the formal investigation on the ground and relies on the little information provided by the Egyptian and Russian authorities, the officials said there was no definitive evidence yet to indicate a deliberate explosion.
“There’s not one thing that we know what is saying to us, ‘This is a bomb,’ ” said one of the American officials, who like others spoke on the condition of anonymity because they were discussing intelligence considered preliminary and classified. “It’s just all indications of this or that, and not clear right now.”
After a meeting of British ministers and security officials in London on Wednesday evening, Philip Hammond, the foreign secretary, said in a statement that the government had reviewed all the available information from multiple sources. “As a result of that review we have concluded there is a significant possibility that the crash was caused by an explosive device on board the aircraft,” he said.
The government also advised against all air travel to Sharm el Sheikh. As many as 20,000 Britons are at the resort, officials estimated.
“Passengers who are on the ground in Sharm el Sheikh will be returned to the U.K.,” Mr. Hammond said. “We are working with the airlines, and the Egyptian authorities put in place emergency procedures and additional screening and additional security” to get those travelers home.
The decisions were announced on the eve of a meeting in London between Mr. Cameron and the Egyptian president, Abdel Fattah el-Sisi. Egypt’s foreign minister, Sameh Shoukry, said in an interview on CNN later that he was “somewhat surprised” by the flight suspension. “It is premature to make statements about what might or might not have happened,” Mr. Shoukry said.
On Tuesday, Mr. Sisi dismissed as “propaganda” a claim of responsibility for the crash by an Egyptian affiliate of the Islamic State.
“The prime minister called President Sisi yesterday evening to discuss what measures the Egyptians are taking to ensure the tightest possible security arrangements at Sharm el Sheikh airport,” Mr. Cameron’s office said in a statement. “While the investigation is still ongoing, we cannot say categorically why the Russian jet crashed. But as more information has come to light we have become concerned that the plane may well have been brought down by an explosive device.”
Mr. Cameron’s office said it had received an initial assessment of the security arrangements at Sharm el Sheikh airport from British security experts late Wednesday afternoon.
“The team noted that the Egyptian authorities had stepped up their efforts but that more remains to be done,” the statement said, adding, “The safety of British citizens will always be our first priority, and in light of the latest picture about what may have caused the crash, we are clear that this is the right thing to do.”
Russians and Egyptians are still investigating the cause of the crash. On Wednesday, an Egyptian affiliate of the Islamic State seemed to gloat about the alarm its claim of responsibility had created, even without corroborating evidence that the group had brought down the plane.
“Die of your rage,” a spokesman for the militant group declared in an audio statement circulated on social media. “We are not forced to disclose the mechanism of our downing it. So you may bring the wreckage of the plane and search it, and you may bring your black box and analyze it. Report to us the conclusions,” the spokesman continued, challenging the international investigators to “prove that we did not bring it down.”
The Islamic State, also known as ISIS or ISIL, and its Egyptian affiliate typically provide video of their attacks or share other details to substantiate their claims of responsibility. But the vague statement on Wednesday, and other details, appeared to suggest that the crash had been caused by terrorism even before any conclusive evidence was released by investigators.
“It sounds a bit like a taunt,” Shadi Hamid, a researcher at the Brookings Institution who studies Islamist movements, said of the militant group’s claims. “ISIS in a sense has already won the public back-and-forth because enough people suspect that ISIS may have done it, and for a group like ISIS the objective reality doesn’t matter — it is a propaganda war.”
The Egyptian Ministry of Civil Aviation said in a statement on Wednesday that information from the plane’s flight data recorder had been extracted from the wreckage and was being analyzed by investigators. “The cockpit voice recorder is partially damaged, and a lot of work is required in order to extract the data from it,” the ministry said. “Consequently, no further comment on the content of the C.V.R. can be made. Examination of parts on site is continuing.”
But a European official who has been briefed on the inquiry said that while the flight data recorder was readable, there appeared to be very little usable information. The official, who spoke on the condition of anonymity because of the sensitivity of the investigation, said it was still not possible to determine what might have caused an explosion.
The official said investigators remained hopeful that data from the cockpit voice recorder could still be recovered. However, it, too, could have shut off because of a blast, the official said.
Because of an editing error, an earlier version of this article referred incompletely to the British government’s action. Britain suspended flights to and from — not just to — Sharm el Sheikh.