An ISIS chemical weapons expert was captured by US Special Forces last month. In picture: A member of the Kurdish peshmerga forces stands is seen atop a tank on the outskirts of Kirkuk March 15, 2015. Iraqi Kurdish authorities said on Saturday they had evidence that Islamic State had used chlorine gas as a chemical weapon against their peshmerga fighters in northern Iraq in January.Reuters

The top expert of the Islamic State group's chemical weapons programme was captured by the U.S. special forces in Iraq last month, and information elicited from him led to two airstrikes on ISIS' weapons facilities. Iraqi Sleiman Daoud al-Afari used to reportedly work for Saddam Hussein's Military Industrialization Authority. 

The ISIS militant, who was captured by the American Special Operations force, told interrogators how the terror group weaponised sulfur mustard and used it in artillery shells, the New York Times reports. This confirms tests by the Organisation for the Prohibition of Chemical Weapons (OPCW) that showed ISIS used mustard gas as a chemical weapon,  the first time since the fall of former Iraqi ruler Saddam Hussein that the chemical agent was used in the country. 

Saddam Hussein, who al-Afari worked for, had used the gas against Iraq's Kurdish community in the 1980s, which left hundreds dead. 

The Pentagon did not confirm al-Afari's detention, who is believed to have been captured by the U.S. Special Operations force comprising the Delta Force commandos. Earlier this month,  United States' Special Operations forces reportedly captured a "significant" ISIS operative in Iraq and were holding him at a temporary detention facility in Erbil. It is not clear if the captured person was al-Afari.

The International Committee of the Red Cross told NYT it had visited the Iraqi ISIS militant in detention. The United States has said it will not hold the detainee indefinitely and will reportedly hand him over to either the Iraqi or the Kurdish forces. 

However, interrogators have received crucial information from the detained ISIS fighter that led them to carry out airstrikes on a weapons production plant and a tactical unit of the Islamic State group in and near Mosul. 

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