The U.S. is concerned that militants could get their hands on any undeclared chemical weapons in Syria. “Certainly if there are chemical weapons left in Syria, there will be a risk that those weapons fall into ISIL’s hands. And we can only imagine what a group like that would do if in possession of such a weapon,” says United Nations Ambassador Samantha Power. She spoke after the UN Security Council heard a briefing by Sigrid Kaag, the head of the UN mission overseeing the destruction of Syria’s chemical weapons. Kaag told the council that 96% of Syria’s declared stockpile has been destroyed, including all of the most lethal chemical agents: 581 metric tons of the sarin precursor methylphosphonyl difluoride and 19.8 metric tons of sulfur mustard. But she says discrepancies and questions remain about what the Syrians declared. Syria agreed last year to give up its chemical weapons, averting possible air strikes by the U.S. military. The move followed global outrage over a sarin gas attack near Damascus in August 2013 that killed hundreds of civilians.