The U.S. Department of Labor is investigating allegations that former Paramount labor relations executive Stephen Koppekin embezzled money from three of the union pension and health plans that he served on as a management trustee. Two years ago, Paramount announced that Koppekin had retired after many years as the studio's SVP Labor Relations. On Thursday, however, the studio acknowledged that he'd been fired for the allegedly embezzlement. "As soon as this was brought to…