Outraged lawmakers are demanding that the Barack Obama administration review its humanitarian effort in Syria following reports that Islamic State (IS) militants have been distributing UN aid packages as their own.

Four House members wrote to the US Government Accountability Office earlier this week to ask that the government auditor examine the mechanisms in place to limit waste and diversion. The request comes after jihadist websites displayed images of militants handing out what appear to be World Food Program packages crudely covered with the IS logo.

“In the increasingly challenging and dangerous environment posed by the Syrian civil war, we are concerned that assistance funds intended for Syria may not be reaching intended recipients,” the lawmakers wrote in a letter to Comptroller Gen. Gene Dodaro obtained by Al-Monitor. “Given these concerns, we request that your office review U.S. humanitarian assistance efforts undertaken in response to the Syrian crisis.”

The letter was signed by Reps. Ileana Ros-Lehtinen, R-Fla., and Ted Deutch, D-Fla., respectively the chairwoman and the top Democrat of the Middle East panel, as well as by panel members Reps. Gerald Connolly, D-Va., and Ron DeSantis, R-Fla.