Hanover, Germany, Sha'ban 1, 1436, May 19, 2015, SPA -- The discovery a 250-kilogramme World War II bomb in Hanover on Tuesday forced the evacuation of 31,000 residents from the central German city, authorities said, according to dpa. Disposal experts were set to try and defuse the bomb around midnight (2200 GMT) at the earliest, a fire department spokesman said. The ordinance had laid buried undetected for 70 years on the grounds of a former high school and adult education centre until it was discovered Tuesday during demolition work at the site. Hanover is the capital of the state of Lower Saxony, and among the areas cleared ahead of the planned disposal was the state parliamentary building. Unexploded bombs dating back to the aerial bombardments of Germany during World War II are still frequently found. Many local authorities have teams working full-time to detect and defuse them. The biggest evacuation in Germany since the end of the war occurred in 2011, when 45,000 people were forced to temporarily leave parts of Koblenz for the disposal of an unexploded Allied bomb. --SPA 00:12 LOCAL TIME 21:12 GMT www.spa.gov.sa/w