BELGRADE, Serbia-The U.S. Embassy in Belgrade says American and Serbian officials are cooperating on an investigation of a U.S. citizen who allegedly committed war crimes here during World War II.

The embassy says U.S. Department of Justice investigators met with Serbian war crimes prosecutor this week to discuss the case of 86-year-old Peter Egner.

The Serbian war crimes court has opened a genocide investigation accusing Egner of serving in a Nazi unit that killed thousands of Jews, Serb and Roma during WWII Nazi occupation of Belgrade.

Egner emigrated to the United States in 1960 and now lives in the Seattle area. The U.S. Justice Department demanded in July that Egner's U.S. citizenship be revoked.