The city authorities announced on Wednesday evening that people would have to be evacuated while the unexploded ordnance found in Siegburger Straße, in the Cologne-Poll quarter, was safely defused and removed, reported local paper Rheinishe Post.
Around 2:24 am authorities said the bomb, which was said to be an American one, had been diffused and residents could return to their homes.
A radius of one kilometre was put in place around the latest bomb discovery, while experts got to work on defusing it – a job that took several hours.
Around 10,000 residents situated within the radius had to leave their homes, including sick and elderly people who had to be transported from their houses and apartments. Care homes and refugee shelters were also affected.
The city had set up three contact points for the residents: the Mudra Barracks, and two schools: Förderschule and Realschule Köln-Deutz.
A total of 1,000 people were accommodated in these facilities and supplied with drinks and snacks. Other residents went to relatives or friends' homes while bomb disposal experts dealt with the discovery.
More than 100 law enforcement and transport workers were on site to assist people.
Employees from the German Red Cross, the police, fire brigade and Bundeswehr (German army) were among those who helped out by assisting people during the evacuations.
Gaja the dog and her owner, just two of the evacuees in Cologne, in the Mudra barracks. Photo: DPA
Eyewitnesses in the barracks reported that the evacuation had been done professionally. The atmosphere was relaxed and there had not been any long queues, they said.
Early on Thursday morning, Cologne City press officers posted a statement saying the bomb had been diffused.
“The bomb has been deactivated and can now be removed,” they said. “All restrictions are lifted and residents can return to their homes.”
Due to the bomb discovery, a number of roads were closed and public transport was affected, including tram line 7 and a freight line.
Autobahn A4 was closed between Vingst and Cologne South, but on Thursday morning authorities said it had re-opened.
More than 70 years after the end of World War II, unexploded devices remain scattered around Germany, a legacy of the intense Allied bombing campaign against the Nazi regime.
In Cologne, a bomb was found recently in the river Rhine due to low water levels caused by a drought.