I would imagine applying water cooling would have a disasterous effect. At some point extinguishing the fires and cooling the 1400 deg C molten steel might be a good idea as the building structure is not designed to withstand that sort of temperature. Concrete floors dont like heat, any moisture or air bubbles and it has a tendancy of throwing parts of itself around the building. There is also an elastic point at which the buildings roof I beams will beging to sag and the roof collapse in on itself. I have seen what happened in a food factory packing hall when a pallet took fire inside a shrink wrap oven, it was made worse by the forklift driver attempting to take the burning pallet outside. In that incident the i beam spans in the roof got so hot they sagged and touched the floor in the middle of the factory.
Its gonna be a bitch to clean up, like 6" steel plate encapsulating everthing, Its got to be a shutdown to gas axe all the crap out of there.