A group of U.S.-trained rebels that recently returned to Syria says it is investigating reports that one of its members has defected and handed over his weapons to the al-Qaida affiliate in the country.

The reports first circulated on social media after the group of about 70 rebels returned to Syria last week. They were armed and trained by the U.S. in Turkey.

On Wednesday, the group known as Division 30 posted a statement on its Facebook page saying if allegations are true, it will refer the officer in question to a military tribal on charges of treason, but that it has so far been unable to contact him.

The U.S. Central Command confirmed Monday the graduates had re-entered Syria with their weapons and were operating alongside anti-Islamic State forces.