A US official says the military is carrying out tests to find out if a chemical agent was used in a ISIL rocket attack on US forces in Iraq. The rocket landed near an airfield on outskirts of the northern town of Qayyarah on Tuesday.

The military official said the first of two field tests showed the presence of a mustard agent but the second did not. The sample has been sent to a laboratory for more reliable testing. The official said no personnel showed any signs of exposure to chemical weapons.