A spokesman for the Iraqi Kurdish forces says a number of their fighters have tested positive for mustard gas after battles with the Islamic State group in northern Iraq.

Jabar Yawar tells The Associated Press that blood samples from the Kurdish Peshmerga fighters sent to a Baghdad lab revealed traces of the toxic gas.

He said Wednesday the exposure took place during the battles around the town of Makhmour.

He says forces from the U.S.-led coalition helping Iraqis also conducted blood and soil samples in the same area and that those also tested positive.

Yawar didn't say how many were exposed.

No one from the coalition was immediately available for comment.

A senior U.S. military officer said in August that preliminary tests showed traces of mustard gas on IS mortars.