MAREA, Syria, Nov. 8 (UPI) -- The United Nations has confirmed that both mustard and chlorine gas have been used in attacks during the Syrian civil war.
The U.N.'s Organization for the Prohibition of Chemical Weapons (OPCW) said it has "utmost confidence" mustard gas was used on Aug. 21 in the town of Marea during fighting between Syrian rebels and the Islamic State.
The Islamic State is accused of using the gas, which "very likely" killed a baby. The OPCW investigated after hearing of the claim and later collected samples and interviewed two people affected by the exposure, as well as their doctors.
"In this case, the team was able to confirm with utmost confidence that at least two people were exposed to sulfur mustard, and that it is very likely that the effects of this chemical weapon resulted in the death of an infant," the OPCW said in a statement.
Sulfur mustard gas can cause skin blistering, blindness, internal and external hemorrhaging, blindness and lung failure.
The OPCW does not say who is responsible for the attack. Witnesses said they were shelled from locations held under IS control.
The OPCW also investigated the potential use of toxic chemicals in an attack in March in the northwestern Idlib province.
The team "concluded that the alleged incidents likely involved the use of one or more toxic chemicals -- including chlorine -- as a weapon."
The regime of Syrian President Bashar al Assad has also been accused of using chemical warfare. The OPCW has set up a team to investigate who is behind the gas attacks.