Vernon fire officials were trying to determine the source of a fire that sent smoke billowing through the upper floors of the Farmer John meat packing company. Fire Capt. David Telford said investigators were “almost 100% sure” that the blaze started in an area where workmen had earlier used a cutting torch. Smoke from the fire poured through the second and third floors of the sprawling one-square-block plant, overcoming three employees. One employees was treated at White Memorial Hospital, the other at County-USC Medical Center. A third employee was treated at the scene.