Builders stumbled upon an unexploded bomb close to Düsseldorf Airport on Wednesday evening, meaning that 8,000 people had to leave their homes on Thursday morning while several major roads were closed.
The 250-kilogram dud explosive from the Second World War was found during construction works in a northern district of the city.
City authorities decided to set up an evacuation perimeter of one kilometre around the find, leading to the order that 8,000 people leave their homes on Thursday morning.
Road blocks were set up to secure the area, barring people from entering the exclusion zone. The operation to bring all those to safety who weren't able to leave the area of their own accord started at 7am on Thursday morning.
A hotel with about 250 guests was also evacuated during the night. Those who worked within the exclusion zone were not able to reach their offices on Thursday.
On Wednesday evening the A52 motorway was shut down in the north of the city, while the A44 was also closed on Thursday morning.
"There will almost certainly be traffic chaos," said a spokesperson for the city council.
On Thursday morning Düsseldorf Airport was only accessible via detours. In a statement the airport asked all travellers to add an extra two hours onto their journey time.
The diffusion of the bomb is expected to start as soon as the danger zone has been cleared.
"We expect that the diffusing will take place in the early afternoon," said the city spokesperson.
Police disclosed that the bomb had a chemical-mechanical detonator, which is "relatively dangerous", adding that they haven't yet decided whether to explode it on site or take it away.
More than 70 years after the end of the war, unexploded bombs are regularly found buried in German soil, a legacy of the Allies' intense bombing campaigns against Nazi Germany.
Last Christmas, 54,000 people were evacuated
from southern Germany's Augsburg city, after the discovery of a 1.8-tonne WWII-era unexploded bomb.