EDIT: It appears that the press release was referring to 122mm Grad rockets, not chemical weapons.
In a 7 April press release, rebel Islamist faction Jaysh al-Islam stated that one of its field commanders used "unauthorized weapons," while fighting YPG/YPJ forces in Aleppo city. While not explicitly stating what the weapons were, Kurdish sources have reportedrebel use ofchemical weapons in their bombardment of Sheikh Maqsud, an ethnically Kurdish neighborhood in Aleppo.
Sheikh Maqsud is the only territory administered by the Kurdish Democratic Union Party outside northeastern Syria and Efrin Canton. Over the last several months, the neighborhood has been subjected to what appears to be indiscriminate bombardment by various rebel factions, reportedly resulting in many civilian deaths.
Over the last week, street fighting between the YPG/YPJ and various rebel factions appears to have escalated, particularly around Castillo Highway, the road that connects rebel-held Aleppo to the rest of rebel territory. The commander of the FSA Northern Division (made up of Liwa Fursan al-Haq and the 101st Infantry Division) was killed two days ago, while the YPG lost a military commander the same day. SAA airstrikes have been reported in the vicinity of fighting, leading to further rebel accusations of the PYD and its militias being allied with the Government.