The discovery of an unexploded bomb from World War II has forced the evacuation of thousands of residents of Munich, Germany, fire officials said. Diffusing the 250-kilo bomb has proved more difficult than experts originally believed, the Web site Sueddeutsche.de reported Tuesday. The device was discovered under one of the city\'s most notorious bars. A fire department spokesman said the bomb could go off at any time. At first authorities thought it would be easy to diffuse but evacuations were ordered after discovering the bomb had a chemical, delayed-action detonator. A controlled explosion was being planned for Tuesday evening, The Local.de reported.