WASHINGTON (AP) — The U.S. is looking into whether a toxic chemical was deployed on areas of Syria that are controlled by rebel forces seeking to oust Syrian President Bashar Assad.

State Department Jen Psaki said Monday the chemical was likely chlorine, if it was used.

This photo provided by the anti-government activist group Aleppo Media Center (AMC), which has been authenticated based on its contents and other AP reporting, shows Syrian men inspecting the rubble of houses that were destroyed by Syrian government forces air strikes in Aleppo, Syria, Monday, April 21, 2014.

She said officials are still trying to determine what happened in the village of Kafr Zita, but that the U.S. takes allegations about chemicals used in combat very seriously.

On Sunday, French President Francois Hollande told Europe 1 radio station that he has "several elements" suggesting recent use of chemical weapons in Syria, but no definitive proof.

Psaki said the U.S. is working with the United Nations and the Organization for the Prohibition of Chemical Weapons to get more details.