The U.S. is investigating what it believes are “credible” reports that ISIS fighters used mustard agent in an attack against Kurdish Peshmerga this week, causing several of them to fall ill, according to U.S. officials working in at least three separate parts of the Obama administration.
All of them strongly emphasize more intelligence is being gathered on exactly what may have happened near the town of Makhmour in northern Iraq.
While there have been accounts posted in social media about the incident, the officials say they have independent information that strongly lead them to assess there was a use of chemical weapons.
The officials would not tell CNN what evidence led them to this belief.
The officials emphasized the intelligence indicates it was likely a small amount of chemical agent and a low concentration.
U.S. officials are concerned, but this is not considered to be a massive attack.