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.

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