Around 31,000 residents in the northern German city of Hannover are being forced to temporarily evacuate their homes after an unexploded World War II bomb was found underneath a former high school on Tuesday afternoon.

The bomb was discovered during the demolition of the former school building. Experts decided, based upon its condition, it needed to be immediately defused and removed and surrounding residents had to be evacuated as a precaution, the DPA news agency reported.

About 850 personnel from the fire department, police, relief organizations and explosives experts were reportedly involved in the operation.

Even 70 years after the end of World War II, unexploded bombs are still found relatively frequently in Germany, generally during construction in major cities.

Hannover was a regular target for Allied bombers during the war. In one raid in 1943 alone, some 261,000 bombs were dropped on the city.

Another unexploded bomb had been discovered near the city in the last September, resulting in up to 14,000 people being evacuated from their homes.