Islamic State militants may have used chemical weapons in an attack in Syria said Medecins Sans Frontieres (MSF) on Tuesday.
The organisation said that it had treated four civilians who suffered from breathing difficulties after a shell hit their home on Friday.
The Syrian American Medical Society also reported receiving 50 patients with symptoms of chemical exposure.
Earlier this month the US confirmed that it suspected Islamic State militants had used chemical agents in attacks against Kurdish forces in northern Syria.