PN. When was this, 1950s? There have been examples of hasty, incomplete clearance, particularly those carried out in immediate post war years by 'colonial' troops in a hurry for the boat home; and who can blame them. Airfield denial with a grid of sunken explosives filled pipes was a classic example.
Let me just correct my remark 'my experience is +25 years'. Sounds a bit flashy expert, which I am not. What I should have said is my experience with mustard gas was +25 years ago.