The US State Department Deputy Spokesman Mark Toner declared that the Islamic State in Iraq and Syria used sulfur mustard chemical weapons in one specific instance in Syria, as well as in Iraq, last year, the Hill reports.
"We believe that the Islamic State for Iraq and the Levant, ISIL, or Daesh, was responsible for a sulfur mustard attack in Marea in August 21st, 2015," State Department Deputy Spokesman Mark Toner said during a briefing.
It is the first time a U.S. official has publicly confirmed that the administration believes ISIS was behind the Aug. 21 attack in Syria.
In addition Toner declared that determination was "largely based on photographic evidence as well as Syrian opposition's description of the event."