The Organisation for the Prohibition of Chemical Weapons (OPCW) has again concluded that the Syrian Air Force used chemical weapons, breaking international law. The OPCW published the findings Jan. 27 in the third report of its Investigation and Identification Team (IIT). The IIT investigates the use of chemical weapons in the Syrian Arab Republic and establishes responsibility. In its latest report, the team used multiple pieces of evidence, including chemical analyses, to conclude that at least one air force helicopter dropped yellow cylinders containing chlorine gas on two apartment buildings, killing 43. “The world now knows the facts—it is up to the international community to take action, at the OPCW and beyond,” OPCW director general Fernando Arias says in a statement.