Builders in the Canadian city of Quebec unearthed an unexploded cannonball fired by the British during their siege of the city in 1759.
The builders posed for photographs by the 200-pound bomb, unaware that it was still potentially explosive, reports CBC.
Municipal authorties contacted archaeologist Serge Rouleau, who took the device to his home and when he realised it could still be live contacted army bomb disposal experts. They removed the device to a safe location where it will be destroyed, or defused and placed in a museum.
"With time, humidity got into its interior and reduced its potential for exploding, but there's still a danger," Master Warrant Officer Sylvain Trudel, a senior munitions technician, told CBC.
"Old munitions like this are hard to predict. You never know to what point the chemicals inside have degraded."
The British besieged the French-held city of Quebec during the Battle of the Plains of Abraham. After the victory the British went on to seize control of the whole of what was to become Canada.
The British fired the cannonball from their positions in Levis, across the Laurentian River from Quebec, reported Le Soleil.
The balls were meant to break apart on impact, releasing gunpowder and a charge and setting fire to buildings.
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