Russia’s security chief said Tuesday a terrorist act brought down the Russian airliner that crashed in Egypt’s Sinai Peninsula on Oct. 31, after revealing traces of explosives were found on board the Airbus A321. Federal Security Service (FSB) Chief Alexander Bortnikov said a homemade bomb equivalent to as much as 2 pounds of TNT exploded and caused the plane to break up in the air, according to state news agency TASS. “I can certainly say that this was a terrorist act,” Bortnikov said. President Vladimir Putin vowed to find and punish those responsible for the attack that killed all 224 people on board, ordering the Russian air force to ramp up airstrikes in Syria in retaliation. The plane, bound for St. Petersburg, crashed about 30 minutes after takeoff from Egypt’s Sharm el-Sheikh. ISIS claimed responsibiliy for the crash shortly after the attack.