When I first saw this on side scan sonar last year I really didn't know what I was looking at as I have never seen anything like it before. I did conclude it was steel/iron due to the hot white areas of the frame showing major sonar reflectivity.
When I dove it recently and saw what it was it of course all made sense then.
Stuck in the mud on edge like a big donut, and sheared off horizontally, this too shows evidence of a bad fire and I believe shows the effects of explosives. Everything was ripped apart not cut with a saw, at least as far as what I looked closely at.
https://youtu.be/_gv4AbBthhU