no injuries reported in blaze at six-alarm fire at louisville appliance facility .
cause for fire , which has drawn 200 firefighters friday morning , unknown .
fire department stretched thin as they also rescue flooded residents .
building , where up to 50 people would normally work , collapsed at 8.30 am .
facility makes appliances such as washing machines , dryers and fridges .
acid particles found in smoke near building , but not in downwind plume .
residents near plant told to close windows , shut off ventilation to outside .