U.S. officials say they have indications that toxic chemicals were used in a rebel area of Syria this month.
White House spokesman Jay Carney said Monday that the alleged attack in the western village of Kafr Zita involved an industrial chemical that was probably chlorine.
The Organization for the Prohibition of Chemical Weapons is working with the United Nations to rid Syria of its declared stockpile of such weapons. The OPCW said this week that 80 % of those chemicals have been removed from the country or destroyed.
U.S. State Department spokeswoman Jen Psaki said Monday that chlorine was not on the list of chemicals that Syria declared last year when it agreed to destroy the arms under international pressure.
Washington and its allies say Mr. Assad's forces unleashed sarin gas last year, killing hundreds of civilians. The Syrian government said it was the opposition fighters who used the chemical weapons.