Firefighters responded to a blaze Wednesday morning at a lumberyard in Ossining.Officials say the fire broke out around 6 a.m. at Melrose Lumber on Croton and Calam avenues. According to officials, about 75 firefighters were needed to battle the blaze.Fire officials say the fire could have been much worse, but the company's sprinkler system was working. Officials say the damage was limited to the company's showroom.Investigators are still trying to determine what cause the fire. Fire officials say that no one was injured in the blaze.