Looks like multiple points of origin from the outside view. That may just be due to the way the fire has developed within the interior.
It doesn’t look like there was much fire in the interior of the building. I would put my money on workers starting a fire on the roof, causing the fake facade to catch fire, spreading across the roof.
It does look that way- from outside- but as you point out- who knows what’s going on inside. Starting to see gray smoke now in some areas- good news!