A neutral Syrian civilian rescue force said barrels of toxic gas were dropped overnight on a rebel-held town close to where a Russian military helicopter was shot down Monday. Five people died in the downed aircraft after it was said to have delivered humanitarian aid to the besieged city of Aleppo. A spokesman for Syria Civil Defence said at least 33 people, mostly women and children, were “affected by the gas,” Reuters reported. “Medium-sized barrels fell containing toxic gasses. The Syrian Civil Defense was not able to determine the type of the gas,” the spokesman said. Workers with the volunteer agency said they believed it was chlorine gas, but could not verify that claim. Representatives from the U.K.-based Syrian Observatory for Human Rights also reported the presence of barrel bombs in the nearby city of Saraqeb. The opposition Syrian National Coalition on Tuesday blamed President Bashar al-Assad’s regime for the attack. Most sides have denied the use of poison gas, including Syria’s government, Russia, opposition forces, and Western powers. The Daily Beast reported Monday that pictures and video of the downed Russian chopper show it was an assault aircraft armed with rockets, calling into question Moscow’s claims that it was on a humanitarian mission.