This is some drywall with scorch marks, left over from the Transformers 3 people when they were filming propane explosions on the roof.
These last two photos are areas where buildings have been completely demolished and harvested for steel. The area in this photo is where the first Banksy (at 555 gallery now) was located, right about in the center of the frame. The City of Detroit has declared that no demolition permits have been issued for the Packard site.
This is another area where large steel buildings have been dismantled and harvested for scrap.
According to the Detroit Free Press and the City of Detroit, nobody has been paying any property taxes on any of the Packard site in over 4 years.