Two contractors were injured in a flash fire Tuesday morning at Carbide Industries in Louisville’s Rubbertown area, fire officials said. The incident was reported around 11:13 a.m. at the plant, 4400 Bells Lane. Officials described the event as a sudden fire involving a 5,000-pound portable tote of calcium carbide. The extent of the contractors’ injuries was not immediately known. Carbide Industries makes calcium carbide, which is used in steelmaking and to produce acetylene gas for welding and cutting. The plant has experienced other serious incidents. An explosion there about a year earlier caused no injuries, while a 2011 explosion and fire killed two people and injured two others.