COLOGNE, Germany — A massive evacuation unfolded in Cologne on Wednesday as authorities defused three unexploded World War II bombs. This operation marked the largest evacuation in the city since the war ended. More than 20,000 residents were ordered to leave their homes after the bombs were discovered during road construction work on Monday.

The bombs included two American 20-ton bombs and one 10-ton bomb, all equipped with impact fuses. City officials reported that the defusing process took about an hour, allowing residents to return to their homes later in the evening.

The evacuation affected a wide area, including 58 hotels, nine schools, a hospital, two nursing homes, and several museums. The Messe/Deutz train station was also closed, along with three bridges across the Rhine River, including the busy Hohenzollern railway bridge. Shipping traffic on the Rhine was suspended during the operation.

Despite the urgency, the start of the defusing was delayed when one resident in the historic center refused to evacuate. City authorities emphasized the importance of safety, as unexploded ordnance from World War II is still frequently found in Germany, necessitating precautionary measures.

Cologne, a city heavily targeted during the war, has a history of such discoveries. The first of 262 Allied air raids occurred on May 17, 1940, and the last bombardment took place on March 2, 1945. Even decades later, the remnants of wartime air raids continue to pose risks, prompting large-scale evacuations when necessary.