Xerox Corp., the world's biggest copier maker, is being sued for allegedly releasing hazardous substances into Pomona's municipal drinking water supply. Xerox said it was served with the suit last month. The suit, filed in Los Angeles County Superior Court, seeks unspecified damages on behalf of 681 people allegedly exposed to the substances through drinking water supplied by Pomona and the Southern California Water Co. The suit against the Stamford, Conn.-based company includes claims for personal injury, wrongful death and negligence. "We deny any liability for the [plaintiffs'] alleged damages and intend to vigorously defend the action," Xerox said in a Securities and Exchange Commission filing.