Stray dogs are very resourceful animals. They are always actively looking for a shelter, or a place to protect themselves from the elements. Therefore, you can always find them in abandoned houses, or warehouses, derelict buildings etc.
While those constructions can protect them from the elements, they can’t protect them from their own structural instability. Namely, many derelict or abandoned houses are themselves very dangerous, are they are usually crumbling all over the place. What’s even worse, is that this makes it even harder to rescue them, as the rescuers have to rist their own safety to get inside.
Just look at how dangerous it can get!