Firefighters are battling hot spots after a massive fire tore through three factory buildings along the waterfront in Sunset Park overnight Wednesday. According to the FDNY, the fire broke out around 12:18 a.m. at 17 53rd St., between First Avenue and a dead end near the Upper New York Bay. Fire officials say much of the building was already on fire when crews arrived, and the flames quickly spread to two nearby factory buildings. Because the fire was so intense, firefighters had to fight it from the outside using tower ladders, large hose streams and FDNY fireboats positioned near the water. At one point, officials say crews were pouring about 15,000 gallons of water per minute onto the fire in an effort to contain it. Video from earlier in the morning showed heavy flames and thick smoke shooting from the buildings as firefighters worked from multiple ladder trucks. Officials say the roof of the original building collapsed, and all three buildings involved have been heavily…..