Several U.S. officials said that on Tuesday, ISIS may have fired a shell with mustard agent that landed at the Qayyara air base in Iraq, where there are U.S. and Iraqi troops. U.S. troops tested it after it landed and believed that they had found the chemical agent mustard. No U.S. troops were hurt or exposed to the agent and one official said the weapon was "low purity" and "poorly weaponized." The substance is being sent to a lab for further examination after one test had a positive result and another had a negative one.
