PHOTOS: Fire officials this week took to social media to remember a firebombing at a local mattress factory that the FBI classified at the time as the “largest arson case” nationwide. Tuesday marked 47 years since an enormous blaze ripped through the B.F. Goodrich Sponge Rubber mattress factory — now, the site of the city’s riverwalk — in one of the biggest industrial arson cases to hit the nation. Fire officials from Shelton’s Echo Hose Hook and Ladder Co. 1 said the fire was set by the factory owners in an effort to collect insurance money. About 700 firefighters from Shelton and surrounding areas battled the 200-foot flames for an estimated eight hours until the blaze was under control on the morning of March 2, 1975. “The FBI labeled it the largest arson case and peacetime bombing in the country,” fire officials said Tuesday.