Emergency workers in Kentucky were increasingly confident that fire crews had contained a blaze spewing flames and smoke from a derailed tanker car, allowing them to focus on untangling other stricken rail cars loaded with toxic chemicals nearby. Hundreds of people remained out of their homes Thursday, including the entire town of West Point and some people from nearby Louisville. The burning butadiene, a chemical commonly found in rubber used to make tires, can damage the central nervous system and reproductive system. Workers were hosing down two other railcars filled with hydrogen fluoride, another corrosive chemical that can cause severe respiratory damage.