The acting U.N. disarmament chief has told the U.N. Security Council that the chemical weapons watchdog has reported the possible use of the deadly nerve agent sarin in an alleged chemical attack in Syria.

Kim Won-soo spoke to several reporters after briefing the Security Council behind closed doors Tuesday on the latest report from the Organization for the Prohibition of Chemical Weapons which includes several outstanding issues.

The report said OPCW investigators who looked at 11 incidents of alleged use of toxic chemicals in Syria came across one instance of blood samples indicating "that individuals were at some point exposed to sarin or a sarin-like substance." It said "further investigation would be necessary to determine when or under what circumstances such exposure might have occurred."