The head of Russia's security service said Tuesday that last month's deadly plane crash in Egypt's Sinai region was a terrorist act and that explosives were found on both the wreckage and luggage from the aircraft.
Federal Security Service (FSB) chief Alexander Bortnikov said the blast came from an improvised explosive device made with up to 1 kilogram of TNT. The FSB also announced a $50 million reward for information leading to the arrest of those responsible.
Russian President Vladimir Putin vowed to find and punish whoever was responsible and called on the country's partners to help identify the culprits.
The Metrojet A-321 flight from the Egyptian resort of Sharm el-Sheikh was headed to St. Petersburg on October 31 when it crashed in the northern part of the Sinai peninsula, killing all 224 people on board.
Militants claiming links to the Islamic State group said they carried out the attack, and a number of foreign governments have expressed their belief that it involved an explosive device.