A team of investigators from the U.S. Chemical Safety Board is deploying to the Carbide Industries plant in Louisville.An explosion Monday evening at the Rubbertown facility killed two workers and injured two others. The CSB is an independent federal agency that investigates chemical industry accidents. Its members are appointed by the president and confirmed by the Senate.Company officials have said only that the blast originated in a furnace. The plant produces calcium carbide, which is used to manufacture acetylene gas and various other chemicals.