The french interior ministry employs a number of people who's full time job is to recover "lost" ammo, bombs, mustard gas, etc etc from WW1 and WW2.
Some years ago, according to the "Smithsonian Magazine" I read about how a group of french loggers, accidently set off an explosion, by starting a campfire to keep warm, unknowingly, that few centimeter below the ground, was a unexploded bomb from WW1 or WW2. Most of these unlucky french loggers died in the explosion.
Also, the fatality rate among the french interior ministry's recovery team is high, and a number og them has also survived mustard gas burns, left over from WW1, according to the same "Smithsonian" article.