Responding to a couple of points above, everybody in the plant got out safely, and one firefighter had some minor injuries.
Precisely because of the concern about runoff, the incident command team made the decision to stop watering the fire, and let the contents of the plant simply burn out. At that point, the building was already a total loss. Even the semi-trailers parked at the loading docks were slag.
The linked article at the top of this thread had several embedded video clips besides the talking head at the scene. In particular, there were several clips taken from a helicopter, fairly widely separated in time, so you can see the progression of the fire even after the fire fighters got to work on it. In the earliest shot (it was down at the bottom of the article when I looked at it), the loading bay area is untouched; in a middle shot, the loading bay is thoroughly on fire inside, but air is still rushing in through the open doorways, pulling flame and smoke back inside, while smoke is just starting to vent from gaps in the wall sheathing and roof. In the latest shot, the loading bay is a mass of flame and the roofs and walls of the trailers parked there are starting to melt from the rear (next to the building) forwards.