As a kid I played in these areas while my dad was cutting wood. It was rather exciting to find a shell as these were rare compared to other pieces of metal. We were just told not to play with them.
I remember that one day we found a shell buried not that far from a fire that my dad had lit.
I was young so I can't certify that we were in a "red zone" but it was in the woods around Verdun so there's a high chance.
"The Real “No-Go Zone” of France: A Forbidden No Man’s Land Poisoned by War" https://news.ycombinator.com/item?id=9609091 http://www.messynessychic.com/2015/05/26/the-real-no-go-zone...