Comment by kayodelycaon

You’re assuming the bombs like this were removed after the war. They weren’t. No one knew they were there.

We are still finding unexploded artillery shells from the first world war in France. Germans are still finding bombs in cities.

The chemicals in the fuses mix and become unstable over time. The explosives don’t degrade as much.

If you wanted further verification, the bomb casing leaves fragments and explosives leave residue.