The World Health Organization said on Wednesday around 500 people had been treated for “signs and symptoms consistent with exposure to toxic chemicals” after a suspected poison gas attack in a Syrian rebel enclave just before it fell. U.S. President Donald Trump and Western allies are considering military action to punish Bashar al-Assad for the reported poison gas assault on Saturday in the town of Douma, which had long had held out against a regime siege. Damascus said reports of a gas attack are false. The WHO condemned the incident and said over 500 people from Douma had been treated for symptoms of gas poisoning. “In particular, there were signs of severe irritation of mucous membranes, respiratory failure and disruption to central nervous systems of those exposed,” it said in a statement issued in Geneva. It cautioned that the WHO has no formal role in forensic inquiries into the use of chemical weapons. International chemical weapons inspectors are seeking assurances from Damascus of safe passage to and from Douma to determine whether globally banned munitions were used, though will not assign blame. WHO also said that more than 70 people sheltering from bombardment in basements in the former rebel pocket of eastern Ghouta, where Douma is located, were reported to have died. It said 43 of those deaths were “related to symptoms consistent with exposure to highly toxic chemicals,” citing reports from its local health partners.