The incident occurred when toxic flammable coke oven gas was released and exploded — fatally injuring two people, injuring 11 others, five of them seriously, and causing an estimated $52.5 million in property damage. During the production process, gases, known collectively as “coke oven gas,” are released and driven off into an off-gas piping system. Coke oven gas is highly flammable, toxic, and colorless with a sulfurous odor. The valve then failed catastrophically, releasing toxic flammable coke oven gas into the surrounding area. The buildings were located less than 20 feet directly above the coke oven gas piping that was the source of the release.