In attacks on Jan. 13, Jan. 22 and Feb. 1, the draft said, government forces fired chemical agents, “most probably chlorine,” into a residential part of eastern Ghouta’s Douma neighborhood, near a sports stadium, roughly 800 yards from the front lines, between 5 a.m. and 6:30 a.m.

Some witnesses described a “slow-acting agent” that smelled like chlorine, the draft said, and they had sufficient time “to rouse the victims, obtain wet cloths to serve as makeshift face masks, and evacuate the affected areas.”

In the Jan. 22 and Feb. 1 attacks, the draft said, the commission had evidence identifying the bomb delivery devices as surface-to-surface industrially produced Iranian artillery rockets, “only known to have been used by Government forces and, rarely, affiliated militias.”

“In relation to the munitions used on 22 January and 1 February, the Commission obtained and assessed material evidence including metadata analysis, and identified a surface-to-surface craft-produced rocket (IRAM). While IRAMs have been employed by a range of actors across Syria, the particular design of observed during these two attacks is only known to have been used by Government forces and rarely, affiliated militias. Specifically, IRAMs documented were built around industrially-produced Iranian artillery rockets known to have been supplied to Syrian Government forces.”

The draft said that the eastern Ghouta attacks had followed “a pattern previously documented by the Commission concerning the use of chemical weapons by Government forces,” and that none of them had suggested “the involvement of armed groups.”

Thirty-one people, including 11 children, were sickened in the first three attacks, but none died. Two other episodes of possible chlorine use, on Feb. 25 and March 7, caused more extensive casualties, killing two children, including an infant, and injuring 18 civilians.

The worst was yet to come, following the collapse of negotiations between Russian military officials and an insurgent group, Jaish al-Islam, to evacuate the Douma neighborhood and end the siege. On April 7, the draft said, an improvised explosive delivered from the air hit a multistory residential building roughly 200 yards from the Rif Damascus Hospital, the last functioning hospital in Douma.

The draft described the explosive as a “single industrial gas cylinder” with fins that struck the top-floor balcony and appeared to have “rapidly released large amounts of a substance into the interior space of the residential apartment building.”

“Positions and physical symptoms displayed by victims of the attack support witness claims that the agent acted rapidly,” the draft stated, “and likely indicate that a high concentration of the chemical sank downwards.”

Based on witness statements and “material evidence received and analyzed by the Commission,” the draft stated, the dead showed “an array of symptoms consistent with exposure to a choking agent, including signs of foaming at the mouth and nose, blue skin indicating impaired blood circulation, meiosis (constriction of the pupils), as well as some cases of dilated (wide open) pupils.”