The State Department ducked questions Friday about a chemical weapons allegation against Jaysh al-Islam, a group that the Obama administration has welcomed to the Syria peace talks in Geneva.

The implication that the group might be involved in the use of chemical weapons has the potential to upend the legitimacy of the talks, especially since the U.S. has maintained a categorical prohibition on the use of chemical weapons. But when asked by reporters on Friday, spokesman Mark Toner said he couldn't confirm if the allegations against Jaysh al-Islam are true.

"I just don't have any information on that," Toner told reporters. "I'll have to look into it."

"Of course we'd be concerned for any group [where there are] serious, credible allegations that they used chemical weapons. We would be concerned about it," Toner said.

Toner additionally declined Friday to comment on how the allegation could affect the peace talks. "I don't want to comment until I have the full picture," Toner said.

Toner did reiterate the department's objection to the Islamic State's apparent use of chemical weapons. "We will continue to hold ISIL accountable for its actions, and that includes any effort to use chemical weapons," he said.

Jaysh al-Islam, or the Islam Army, admitted Friday that one of its commanders engaged in an "unauthorized" attack utilizing chemical weapons in the Syrian city of Aleppo, recently retaken by the armies of Syrian President Bashar al-Assad. The reports emanate mostly from Russian and Chinese media, countries whose governments back Assad.

The U.S. favors a Syrian future without Assad, and has tacitly backed a number of groups in Syria unaligned with the Islamic State, or its principal rival, Assad's government.

Jaysh al-Islam allegedly fired mortar shells consisting of chemical gas into Kurdish-controlled areas in the Sheikh Maksud district in Aleppo on Thursday.

According to reports, Internet video of the aftermath of the attack circulated online, showing how several people were having trouble breathing after the attacks, consistent with a chemical strike. Activists allege that the attack killed nine civilians and injured 29 others.