Almost 23,000 people were evacuated in a town in central Italy after the workers found an unexploded bomb from World War Two during excavation work.
According to the officials in Fano, the British-made bomb might blast after it was accidentally activated.
Patients were removed from a hospital and train services were suspended before the army and navy experts removed the device and dropped it into the sea.
Schools were ordered to remain shut on Wednesday.
The 1.1m (3.6ft) long bomb, weighing 225kg (500lb), was found on Fano's seafront during the construction of a drain.