“It is something we continue to discuss with Russia as well as other members of the ISSG [International Syria Support Group],” Toner said.
On Thursday, a spokesman for Syrian Kurds told Sputnik that gas poisoning cases had been reported among the civilian population and Kurdish militias after an attack on Aleppo by Islamic militants on Wednesday.
The Jaysh al-Islam group took responsibility for the shelling of Aleppo and stated that it had deployed "forbidden" weapons. The group, however, did not specify whether it used chemical agents.
"We will continue to hold Daesh or ISIL [Islamic State] for its actions, and it extends to any efforts to use the WMD [weapons of mass destruction]. It’s not surprising that they would resort to the use of WMD, or rather chemical weapons," Toner noted.
UN Secretary-General Ban Ki-moon said earlier on Friday that the United Nations works closely with the Organization for the Prohibition of Chemical Weapons (OPCW) on the possible use of chemical weapons in Syria, and plans to undertake soon a second investigation into the incident.
Toner pointed out that the United States has full confidence in the OPCW to carry out such probes.