Khan al-Assal chemical attack  The Khan al-Assal chemical attack was a chemical attack in Khan al-Assal, Aleppo, Syria on 19 March 2013, which according to the Syrian Observatory for Human Rights resulted in at least 26 fatalities including 16 government soldiers and 10 civilians, and more than 86 injuries. Immediately after the incident, the Syrian government and opposition accused each other of carrying out the attack, but neither side presented clear documentation. The Syrian government asked the United Nations to investigate the incident, but disputes over the scope of that investigation led to lengthy delays. In the interim, the Syrian government invited Russia to send specialists to investigate the incident. Samples taken at the site led them to conclude that the attack involved the use of sarin, which matched the assessment made by the United States. Russia held the opposition responsible for the attack, while the US held the government responsible. UN investigators finally arrived on the ground in Syria in August (with a mandate excluding the evaluation of culpability for the chemical weapons attacks), but their arrival coincided with the much larger-scale 2013 Ghouta attacks which took place on 21 August, pushing the Khan al-Assal investigation "onto the backburner" according to a UN spokesman. The UN report, which was completed on 12 December, found "likely use of chemical weapons in Khan al-Assal" and assessed that organophosphate poisoning was the cause of the "mass intoxication". A February 2014 report from the UN Human Rights Council stated that the chemical agents used in the Khan-Al-Assal attack bore the "same unique hallmarks" as those used in the 2013 Ghouta attacks. The UN report also indicated that the perpetrators of the Al-Ghouta attack "likely had access to the chemical weapons stockpile of the Syrian military". In neither incident, however, was the commission’s "evidentiary threshold" met in regard to identifying the perpetrators of the chemical attacks. Laboratories working for the Organisation for the Prohibition of Chemical Weapons compared samples taken by a UN mission in the Damascus suburb of Ghouta after the Aug. 21, 2013 attack, when hundreds of civilians died of sarin gas poisoning, to chemicals handed over by Damascus for destruction in 2014. The tests found “markers” in samples taken at Ghouta and at the sites of two other nerve agent attacks, in the towns of Khan Sheikhoun in Idlib governorate on April 4, 2017 and Khan al-Assal, Aleppo, in March 2013. “We compared Khan Sheikhoun, Khan al-Assal, Ghouta,” said one source who asked not to be named because of the sensitivity of the findings.