Atlantic Richfield Co., which was sued last week by nine current and former temporary workers who accused the oil company of misclassifying employees as temporary or contract workers to avoid paying benefits, has responded by saying that the plaintiffs never worked for the Los Angeles-based firm but were all employees of independent oil field service companies. Arco earlier had declined to comment until it studied the suit. Those companies, not Arco, supervised the employees and made all personnel decisions regarding the workers, Arco said. The workers contended in their lawsuit that they were trained and supervised by Arco, which provided their equipment and supplies. Arco said it contracted with established companies and not individuals. The workers said that they were employed by a succession of payroll companies during their time at Arco. Arco said it will "vigorously" defend against the charges. Arco shares rose 38 cents to close at $83.56 on the New York Stock Exchange.