"Islamic State militants likely used mustard agent against Kurdish forces in Iraq this week, senior U.S. officials said Thursday, in the first indication the militant group has obtained banned chemicals."
As NPR's Tom Bowman reports, officials are working to obtain soil samples in order to determine if chemical weapons were used.
"Officials tell NPR the suspected chemical weapons attack occurred earlier this week, part of a mortar barrage in the village of Sultan Abdullah, just south of Mosul.
"Officials said some Kurdish troops showed respiratory troubles that are consistent with chemical weapons exposure. It's uncertain how many Kurdish troops were effected. ...
"Still, one Pentagon source says it's uncertain what, if any chemical was used. And it's possible that it was chlorine. US intelligence agencies have suspected that ISIS has used that chemical in past attacks."