I know there was an "Incident" at Bari (Italy) towards the end - or maybe just after the end - of WW2 involving Mustard Gas.
I don't know the details but apparently a consignment of Mustard Gas Bombs were being either loaded or unloaded from a ship and there was a fire (or some such catastrophe).
Gas escaped and contaminated a large area of the town.
My uncle was in the guard cordon and this was one of his favourite war-stories. He often had difficulty convincing others that we actually had nasty gas-warfare weapons - most thought they had been outlawed after WWI.