Concerns were raised after Kurdish troops suffered “respiratory irritation” after a rocket attack Tuesday, Germany’s Defense Ministry claimed.
Both Germany and Britain have sent hundreds of troops to train Kurdish Peshmerga fighters in northern Iraq in the ongoing battle against ISIS.
The suspected chemical attack on Tuesday is believed to be the first time Islamic State militants have used a chemical missile in a long-range weapons system.
“We have indications that there was an attack with chemical weapons” against Kurdish fighters which left many suffering from “respiratory irritation,” a German Defense Ministry spokesman told AFP.
A senior Peshmerga official said the attack took place 30 miles west of Erbil, the Kurdish capital.
US officials have suggested attackers used mustard gas, which may have been taken from stockpiles of banned chemical weapons which Syrian President Bashar Al-Assad was forced to give up in 2013. But the Peshmerga official said the weapons were made of chlorine.
“Last Tuesday afternoon, Peshmerga forces in the Makhmur area 50km (30 miles) west of the city of Erbil were attacked with Katyusha rockets filled with chlorine,” the official said.
Former officer Hamish de Bretton-Gordon said extremists had been experimenting with chemical weaponry since autumn 2014. He said 15 Islamic State militants were killed during one calamitous experiment.
De Bretton-Gordon added that chlorine gas was rarely fatal when it comes into contact with troops.
Iraqi authorities believe the IS car bomb attack on January 23 was at least partially a chemical attack.
Analysis of fragments of soil and clothing found traces of chlorine, and other explosive devices in the area have also been found to contain the chemical.
In July, the Conflict Armament Research group and Sahan Research group said they believed the Peshmerga had been targeted with chemical weaponry.
The UK Ministry of Defence said: “All military personnel are appropriately prepared prior to deployment.”
There are currently an estimated 275 British troops stationed in northern Iraq.