The Pentagon hopes an ISIS chemical weapons engineer captured in Iraq last month will lead U.S. troops to possible weapons sites and help prevent chemical attacks by the Islamic State.

Defense officials hope that Sleiman Daoud al-Afari will help them find storage sites for chemical munitions including mustard agent, which can blister the skin and lungs and lead to death in high concentrations. Iraqi officials told the Associated Press that al-Afari worked for Saddam Hussein's military and has long been a member of ISIS, which seized portions of Iraq last summer.

Al-Afari's capture has already led to some U.S. airstrikes against suspected ISIS chemical weapons stockpiles, one U.S. national security official confirmed to NPR.

Pentagon spokesman Navy Capt. Jeff Davis declined to confirm the capture of al-Afari but he talked about the chemical threat in general terms.

"We've said before that they have used chemical weapons in both Iraq and Syria, sulphur mustard specifically," Davis said. Anyone who's making and using weapons of mass destruction, particularly a terrorist group like ISIL, would be well advised to know that we don't intend to let them keep doing that."

Al-Afari was captured as part of a new strategy in which Army Delta Force special operators go after Islamic State leaders with the goal of bringing them in and interrogating them about the terror group's operations. American officials are questioning al-Afari but they do not plan to detain him; they expect him to be handed over to Iraqi custody.

Democratic Rep. Adam Schiff, ranking member of the House Intelligence Committee, said the capture and interrogation of al-Afari showed Washington's new approach in Iraq is already paying off.

"While these on-the-ground captures pose real dangers to our troops and can risk bringing the U.S. more fully into this conflict, the rewards can be great in terms of vital intelligence collected, ISIS operations disrupted, and attacks thwarted – including those which may involve chemical weapons," he said in a statement.

Meanwhile, Kurdish officials in northern Iraq reported that this week some 40 civilians suffered from skin irritation and choking after mortar shells with "poisonous substances" were fired into a village south of Kirkuk, which is under Kurdish control.

And separately, Syrian Kurdish officials say jihadists on Tuesday used phosphorous in a chemical attack on the city of Aleppo. Five people remain hospitalized.

There have been numerous reports since last summer of chemical weapons use by ISIS and other jihadi groups. Some of the chemicals have been stolen from old military stockpiles, while others amount to a homemade brew. Also, there is an abundance in Syria and Iraq of chlorine, which is used as a water purifier but can also be weaponized by placing high concentrations into an artillery shell.

Last August, NPR reported on an artillery attack on a village just south of the Iraqi city of Mosul, sickening Kurdish troops.

And recently, on the CBS News show 60 Minutes, CIA Director John Brennan was asked by reporter Scott Pelley about the use of chemical weapons by ISIS:

"Scott Pelley: Does ISIS have chemical weapons?

"John Brennan: We have a number of instances where ISIL has used chemical munitions on the battlefield.

"Scott Pelley: Artillery shells.

"John Brennan: Sure. Yeah.

"Scott Pelley: ISIS has access to chemical artillery shells?

"John Brennan: Uh-huh (affirm). There are reports that ISIS has access to chemical precursors and munitions that they can use."

With ISIS under continual pressure by U.S. airstrikes and local forces, officials said, there are concerns that ISIS could turn more to the use of chemical weapons in desperation.

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