What we know so far about chemical weapons in Syria's civil war Much more is known about an incident on the same day in Khan al-Assal, west of Aleppo. Israel has asserted that the regime fired the nerve gas Sarin, killing 32 people. Reports at the time said Syrian troops were among the dead. At the time, Bashar al-Assad regime accused Islamic jihadist rebels of using chemical weapons. Reports said a home-made locally-manufactured rocket was fired, containing a form of chlorine known as CL17. The opposition has said casualties were caused by a misdirected Syrian air to surface missile, pointing out that none of the rebel groups possess air power. An alleged chemical attack in Aleppo (AP) The Syrian Support Group, the Washington-based representatives of the Free Syrian Army in Washington, said a phosphate similar to sarin was used in that attack. Echothiophate induces similar effects but is not covered by the Convention on Chemical Weapons. The third incident, first reported in the Daily Telegraph, and described in more detail by witnesses to the Times, occurred on April 13 in Sheikh Maqsood near Aleppo. Victims reported a shell landing in a residential area in the middle of the night. Several people died. Doctors who tried to save them say they foamed at the mouth and nose and were in a trans-like state. The Syrian Support Group, based in Washington, has claimed that a chemical agent was used twice in one night on targets in the south of Daraya, with 105 people affected.