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Evidence indicates a bomb brought down Russia's Metrojet Flight 9268 over the Sinai Peninsula last weekend, and U.S. investigators are focusing on ISIS operatives or sympathizers as the bombers, a U.S. official told NBC News on Wednesday.
Questions have swirled over whether foul play or terrorism may have downed the Metrojet-operated Airbus A321 since it crashed in Egypt on Saturday, killing all 224 people aboard. A group claiming to be affiliated with ISIS took credit for the crash via social media media Wednesday.