The investigation followed claims by the rebels that the attack, which reportedly left four people dead and many injured, was carried out by government forces using chlorine gas.
The UN special envoy for Syria STAFFAN DE MISTURA said if the use of chlorine gas is confirmed, the incident would be treated as a war crime.
MISTURA said there was a lot of evidence that it actually did take place, which requires everyone to get together to address the issue immediately.
