Washington (CNN) – ISIS is suspected of firing a shell with mustard agent that landed at the Qayarrah air base in Iraq Tuesday where US and Iraqi troops are operating, according to several US officials.
The shell was categorized by officials as either a rocket or artillery shell. After it landed on the base, just south of Mosul, US troops tested it and received an initial reading for a chemical agent they believe is mustard.
No US troops were hurt or have displayed symptoms of exposure to mustard agent.
One official said the agent had “low purity” and was “poorly weaponized.” A second official called it “ineffective.”
A US defense official said troops had gone out to look at the ordnance after it landed. Based on seeing what they thought was a suspect substance, two field tests were conducted.
The first test was positive and the second was negative, the official said. The substance is now being sent to a lab for further examination.