Police will ring every doorbell and use helicopters with heat-sensing cameras to make sure nobody is in the area before they diffuse the bomb, and anyone who refuses to leave would be forcibly removed.
Bomb technicians had been scheduled to begin work shortly after noon (1000 GMT), but the fire department said there were delays as some people refused to leave.
Authorities in recent days have evacuated residents of nursing homes and hospital patients from the area ahead of today's planned disposal efforts. In Frankfurt, some 60,000 were ordered to leave a 1-mile radius around the site where a 1.8-ton British bomb was to be disposed of Sunday.
The evacuation area includes Germany's central bank which houses half the country's gold reserves.
A steady flow of people filed into a temporary shelter at Frankfurt's trade fair site, with bananas and beverages on offer.
Officials have moved quickly to safely dispose of the bomb, amid concerns that an uncontrolled explosion would destroy an entire block of buildings.
More than 2,000 tonnes of live bombs and munitions are found each year in Germany, even under buildings. Allied forces carried out a heavy bombing campaign, and between 10 per cent and 30 per cent of the bombs that were dropped did not explode.
The Sunday evacuation is the largest seen in Germany since the war.
Roads and transport systems will also be closed, and air traffic in the evacuation zone may be affected.