Updated

Federal officials are investigating after two semi-automatic rifles given to the Des Plaines police department more than a decade ago were discovered missing.

The (Arlington Heights) Daily Herald reports the agency that manages the Defense Department's surplus property program referred the matter to its Office of the Inspector General.

Police Chief Bill Kushner says the department will cooperate "in every possible way."

Des Plaines received a pair of M-16A1 rifles in 2002 through a Department of Defense program that supplies local law enforcement with surplus military equipment.

The police department reported the rifles missing in January after a required weapons inventory.

Kushner said records keeping between 2007 and 2013 was "so muddled and virtually nonexistent" it's been impossible to determine who used the guns and how they were lost.