The Russian government has determined it was a bomb that brought down a Russian plane over Egypt, killing all 224 passengers on board.
"One can unequivocally say that it was a terrorist act," Alexander Bortnikov, head of Russia's Federal Security Service, said at a meeting chaired by Russian President Vladimir Putin. Bortnikov said that "traces of foreign explosives" were found on the wreckage.
The BBC reports that Putin vowed to "find and punish" those responsible for the bomb. He also said Russia must step up its military campaign in Syria.
An affiliate of ISIS claimed responsibility for the crash hours after it occurred on Oct. 31.
The charter flight was en route from the beach resort of Sharm el-Sheikh to St. Petersburg when it disappeared from radar. Nearly all the passengers and crew killed in the crash were Russian nationals.