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.