“There is a definite feeling it was an explosive device planted in luggage or somewhere on the plane,” a U.S. official familiar with the matter told CNN. The official said the bomb was most likely planted by ISIS or an ISIS affiliate, but said the U.S. intelligence community has not reached a formal conclusion.

Other officials also told CNN a bomb appears to have caused the crash on the Sinai Peninsula, which killed all 224 people on board. Senior officials with the Russian company that owns the jet ruled out technical failure or pilot error as the cause Monday.

A British investigation into the crash revealed earlier Wednesday the jet “may well have been brought down by an explosive device.” But a spokesman from Prime Minister David Cameron’s office said it’s too early to “categorically say” why the plane crashed.

Britain suspended flights to and from an Egyptian resort Wednesday, a move The Jewish Chronicle reported may have been based on Israeli intelligence warning of an imminent terror threat.

Autopsy reports on about 150 bodies examined in St. Petersburg revealed passengers in the rear of the jet suffered “explosive trauma,” had shrapnel injuries, and were peppered with metal particles.

ISIS almost immediately claimed responsibility for the crash, but Egyptian leaders initially labeled the claim as “propaganda” and others expressed skepticism the group could bring down the plane.

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