Work on a building in Maella, near Zaragoza in northeastern Spain, was halted after the man said that when he was six-years-old the building was bombed but the device failed to explode.
Metal detectors were used to find the 50 kg bomb which was dropped by the Italian air force, which sided with the Nationalist forces of General Francisco Franco during the 1936-1939 war.
"A local resident alerted the owner of the premises that he had to be careful when carrying out works because during the civil war, when this person was six, the town was bombarded and one of the bombs did not explode. Later concrete was poured on the ground and the artefact was hidden from view," the Civil Guard said in a statement.
Bomb disposal officers blew up the device on Jan. 10, but the operation was made public on Sunday.
(Reporting by Graham Keeley and Silvio Castellanos, Editing by Angus MacSwan)
