According to the report – the fourth from the 13-month-long inquiry by the UN and the Organisation for the Prohibition of Chemical Weapons – investigators found that helicopters flying from military bases dropped barrel bombs containing chlorine gas, a prohibited weapon, the BBC reported.
It said that the helicopter flights could have originated from two bases where the 253 and 255 squadrons, part of the 63rd helicopter brigade, were based.
But the inquiry said that it “could not confirm the names of the individuals who had command and control of the helicopter squadrons at the time.”
It added that those “with effective control in the military units… must be held accountable”.
The report also accused the government forces of carrying out the toxic gas attack in Qmenas in Idlib governorate on March 16, 2015.
The use of chlorine as a weapon is prohibited under the 1997 Chemical Weapons Convention, which Syria joined in 2013.