Texaco said it is closing three of its plants.

The White Plains, N.Y.-based oil company said the closures include two of its oldest U.S. oil refineries and layoffs for about 500 employees because of declining demand for refined petroleum products. It said it was closing its refineries at Amarillo, Tex., and Lawrenceville, Ill., effective immediately. The company said it was also closing its Mount Vernon, Ind., barge terminal, which handles products produced at Lawrenceville for shipment.