WASHINGTON, Sept. 21 (UPI) -- The U.S. military is looking into the possibility that Islamic State militants fired a chemical weapons rocket near an American outpost in Iraq, officials said Wednesday.
A fragment of a mortar shell was found near the U.S. base in Qayyarah, investigators said, and will undergo testing to see if it carries mustard agent residue.
U.S. officials said the Qayarrah West Airfield was targeted by indirect fire on Tuesday and the shell may have been fired then.
Hundreds of servicemen and women are stationed at the base and are preparing it for an upcoming offensive in the militant-held city of Mosul.
No one was injured during Tuesday's fire.
When the fragment was found, it showed a tar-like residue that is often associated with mustard agent, officials said.
The Islamic State has used mustard shells in the past against Iraqi and Kurdish forces.
