Islamic State militants may have used chemical weapons for a second time in an attack on a town in northern Syria.
Medicins Sans Frontieres said Tuesday it had treated Friday four members of a family who suffered from breathing difficulties and developed blisters after a mortar hit their home in Marea, BBC reported.
In addition, the Syrian American Medical Society has reported receiving 50 patients with symptoms consistent with chemical exposure.
“At least half of the 50 mortar and artillery shells fired by ISIS contained poisonous mustard gas,” Hussein Nasir, a spokesman for a Syrian rebel group, the Shami Front, told The New York Times.
Local rebels told the BBC the shells were fired from a village to the east occupied by Islamic State militants.
The latest report comes less than a week after U.S. officials found traces of mustard gas in mortar shells fired by the Islamic State on Kurdish fighters on Aug. 11.
Investigators have not yet officially confirmed whether or not mustard gas was used in the attack, but if it was, their next priority is determining how the terrorist group came into possession of the chemical weapons.
Mustard gas is a chemical warfare agent developed during World War I and banned by treaty in 1993, according to the Centers for Disease Control and Prevention.
Although exposure to the agent is not usually fatal, it can cause blistering of the skin, eye pain and blindness, as well as respiratory problems, the CDC said.