About 20,000 people were evacuated Wednesday in the west German city of Cologne after a 1,000-kilogram bomb dating back to World War II was discovered in the city's north-east, dpa reported. The inhabitants of a retirement home and a home for disabled people had to be evacuated, and the zoo and local schools were closed after the unexploded ordinance was found during maintenance work on an underground heating system. The bomb is expected to be defused in the afternoon.