While it was initially unclear which chemicals had been used, in 2019 the OPCW FFM (Fact-Finding Mission) report concluded: "Regarding the alleged use of toxic chemicals as a weapon on 7 April 2018 in Douma, the Syrian Arab Republic, the evaluation and analysis of all the information gathered by the FFM—witnesses’ testimonies, environmental and biomedical samples analysis results, toxicological and ballistic analyses from experts, additional digital information from witnesses—provide reasonable grounds that the use of a toxic chemical as a weapon took place. This toxic chemical contained reactive chlorine. The toxic chemical was likely molecular chlorine."
[1]:9.12 The OPCW said it found no evidence to support the government's claim that a local facility was being used by rebel fighters to produce chemical weapons