The wreckage of a A321 Russian airliner in Wadi al-Zolomat, a mountainous area of Egypt's Sinai Peninsula. Russian airline Kogalymavia's flight 9268 crashed en route from Sharm el-Sheikh to Saint Petersburg on October 31, killing all 224 people on board, the vast majority of them Russian tourists. AFP PHOTO / RUSSIA'S EMERGENCY MINISTRY / MAXIM GRIGORYEV
*RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RUSSIA'S EMERGENCY MINISTRY / MAXIM GRIGORYEV" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS *MAXIM GRIGORYEV/AFP/Getty Images
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The wreckage of a A321 Russian airliner in Wadi al-Zolomat, a mountainous area of Egypt's Sinai Peninsula. Russian airline Kogalymavia's flight 9268 crashed en route from Sharm el-Sheikh to Saint Petersburg on October 31, killing all 224 people on board, the vast majority of them Russian tourists. AFP PHOTO / RUSSIA'S EMERGENCY MINISTRY / MAXIM GRIGORYEV *RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / RUSSIA'S EMERGENCY MINISTRY / MAXIM GRIGORYEV" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS *MAXIM GRIGORYEV/AFP/Getty Images
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The wreckage of a A321 Russian airliner in Wadi al-Zolomat, a mountainous area of Egypt's Sinai Peninsula. Russian airline Kogalymavia's flight 9268 crashed en route from Sharm el-Sheikh to Saint Petersburg on October 31, killing all 224 people on board, the vast majority of them Russian tourists. AFP PHOTO / RUSSIA'S EMERGENCY MINISTRY / MAXIM GRIGORYEV
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Story highlights

U.S. intelligence is suggesting an ISIS or ISIS affiliated bomb caused the downing of plane last week

The official stressed there has not been a formal conclusion

(CNN) —  

The latest U.S. intelligence suggests that the crash of a Russian passenger jet in the Sinai over the weekend was most likely caused by a bomb on the plane planted by ISIS or an ISIS affiliate, according to a U.S. official familiar with the matter.

But the official stressed a formal conclusion has not been reached by the U.S. intelligence community.

“There is a definite feeling it was an explosive device planted in luggage or somewhere on the plane,” the official, who is familiar with the latest U.S. intelligence analysis of the crash, told CNN.

Other U.S. officials also told CNN that the analysis is pointing toward the cause being a bomb.

Based on the same intelligence, the U.S. belief is that ISIS or an ISIS-affiliated group is responsible for the attack, the official said.

The British government announced Wednesday that it had “become concerned that the plane may well have been brought down by an explosive device.”

The British government did not detail precisely how it reached that conclusion. But a UK aviation team is traveling to inspect the Sharm airport to look at whether there were proper security measures at the airport and the various scenarios, by which, an explosive device could have made it to the Russian airliner “including a person or in cargo,” according to the British transport minister.