Kurdish officials are working with the U.S.-led coalition to verify if Islamic State militants hit Kurdish peshmerga fighters with chemical weapons in the northern area of Sinjar.
Dozens of peshmerga as well as civilians reported suffering from nausea and vomiting after homemade IS rockets hit the area.
The Kurdistan Region Security Council said on its Twitter feed that it was investigating the February 25 attack.
If confirmed, according to the Kurdish authority it would be the eighth chemical weapon attack on its forces.
U.S. Director of National Intelligence James Clapper told Congress in early February that the extremist group had used chemical agents in both Iraq and Syria.
CIA Director John Brennan later confirmed that IS had the ability to manufacture both chlorine and mustard gas.
A source at the Organization for the Prohibition of Chemical Weapons told Reuters earlier in the month that lab tests showed Kurdish fighters had been exposed to mustard gas last year.