Bomb disposal experts on Sunday defused two World War II bombs after the evacuation of about 45,000 people from their homes in the western German city of Koblenz, officials said.

A 1.8-tonne British bomb and a smaller US bomb were successfully de-activated, the fire service said, after their discovery in the River Rhine when water levels fell due to a long dry spell.

Nearly half of the population had been ordered to leave their homes within a 1.8-kilometre (one-mile) radius of the site, including from two hospitals, seven old people’s homes and a prison.

As well as the bombs, the second of which weighed a 125 kilograms (275 pounds), a drum of chemicals also dating from the World War II and found nearby had to be made safe.

Hundreds of people had to be driven in emergency and disabled vehicles out of the evacuation zone earlier in the day, authorities said.

After the all-clear was given to return following the bombs’ defusal, about 650 then had to be ferried back.

Nearly 100 patients had been transferred on Saturday to other hospitals.

The evacuation was handled by 2,500 fire, police, medical and technical personnel as well as city officials. Seven schools were made available for shelter.

Loud-speaker announcements made from vehicles earlier warned residents to leave.

But leaflets had already been distributed advising “Please lock your houses/flats, close your windows and, if possible, leave the shutters on the windows down”.

“Please think to take any necessary medication in sufficient quantity,” the leaflet read.

Streets had been closed off and the main train station was earlier shut to trains.

Residents had spotted the British bomb from their balcony and had informed authorities, Welt am Sonntag reported.

More than six decades after the war, authorities believe there are still some 3,000 bombs buried beneath the capital Berlin alone, and unexploded devices are regularly discovered in construction work.

In June 2010, a 500-kilo Allied bomb, thought to be British, exploded and killed three German sappers and seriously injured two others in the central city of Goettingen as they prepared to defuse it.