[FReepaholic]

Here's an interesting image:

Now, were the holes in the large building on the left made by falling debris (rail cars) or explosions???

[Robert A Cook PE]

I'd say falling debris ...

The top of the building is otherwise very "clean" and still is white, almost untouched.

If it (the missing roof sections) were thrown "up" from inside, then more debris would be closely scattered around the holes.

Instead, if a large falling piece of rail car more or less straight down onto the roof, then the debris would fall inside the building through the same hole.