US probes 'so-called Islamic State chemical shell attack' on American troops in Iraq

So-called Islamic State fired a shell that may have contained a mustard agent onto a military base in Iraq used by US and Iraqi troops, officials told American media.

CNN reported that the shell was either a rocket or an artillery shell, and that an initial test on it gave a reading for a chemical agent they believe is mustard. However, a second test gave a negative reading for chemical agents.

No troops were injured in the attack at the Qayyarah air base in northern Iraq, and did not show symptoms of exposure to chemical weapons, such as skin blistering, it was reported.

All those involved went through decontamination showers as a precaution.

One official told CNN that the agent had a "low purity" and was "poorly weaponised", while another called it "ineffective".

The officals added they "had expected" that so-called Islamic State might try to use chemical weapons as US and Iraqi forces push towards Mosul in an attempt to take back the city.

Several hundred US troops use Qayyarah as a staging are for supporting Iraqi forces.