US investigating whether ISIL used chemical weapons

Alistair Baskey, a spokesman for the White House's National Security Council, said the U.S. is taking the allegations "very seriously" and seeking more information about what happened. He noted that ISIL had been accused of using such weapons before.

"We continue to monitor these reports closely, and would further stress that any use of chemicals or biological material as a weapon is completely inconsistent with international standards and norms regarding such capabilities," Baskey said in a statement.

ISIL could have obtained the mustard agent in Syria, whose government admitted to having large quantities of the blistering agent in 2013, when it agreed to give up its chemical weapons arsenal, The Wall Street Journal reported.

Earlier Thursday, Kurdish officials said their forces, known as peshmerga, were attacked the day before near the town of Makhmour, not far from Irbil. Germany's military has been training the Kurds in the area, and the German Defense Ministry said some 60 Kurdish fighters had suffered breathing difficulties from the attack — a telltale sign of chemical weapons use. But neither Germany nor the Kurds specified which type of chemical weapons may have been used.

Confirmation of chemical weapons use by ISIL would mark a dramatic turn in the U.S.-led effort to rout the group from the roughly one-third of Iraq and Syria that it controls.

Although the U.S. and its coalition partners are mounting airstrikes against the ISIL, they are relying on local forces like the Kurds, the Iraqi military and others to do the fighting on the ground. Already, those forces have struggled to match the might of the well-funded and heavily armed extremist group.

U.S. intelligence agencies have said in the past they believed ISIL has used chlorine gas in attacks in Iraq, the Journal reported. Chlorine is not a banned chemical agent.

The Organization for the Prohibition of Chemical Weapons, the global chemical weapons watchdog, has been investigating possible undeclared chemical weapons stockpiles in Syria.

Wire services