The United States is looking into reports that chemical weapons have been used in two separate attacks in Syria.
More than 100 people are said to be suffering from severe respiratory damage in the Idlib town of Telminnis, according to both the Syrian opposition and government.
Barrel bombs containing chlorine gas are alleged to have been dropped by helicopter.
White House spokesperson Jay Carney said the US was trying to verify claims: “We have indications of the use of a toxic industrial chemical, probably chlorine, in Syria this month in the opposition dominated village of Kafr Zeita. We are examining allegations that the government was responsible. We take all allegations of the use of chemicals in combat very seriously. And we are working to determine what happened.”
The Syrian government says chlorine gas has been used in the Hama province town of Kafr Zeita, but was unleashed by the al-Qaeda linked Jabhat al-Nusra.
Two people are said to have been killed and dozens contaminated by the chlorine.
Chlorine is not listed as a chemical Syria must to give up under the Security Council resolution. But its use as a weapon of war is banned under the Chemical Weapons Convention.
The Syrian government failed to meet the Feb 5 deadline to remove all chemical weapons and precursors from its territory, Damascus has since agreed to shift all stocks by late April.