4,000-pound, World War II bomb forces mass evacuation in Germany

Update 1:20 p.m. ET

BERLINGerman authorities safely defused a huge bomb left over from World War II after evacuating large parts of the western city of Dortmund on Sunday.

More than 20,000 people were evacuated from their homes in Dortmund as authorities prepared to take action following the bomb's discovery.

The 4,000-pound bomb was uncovered after experts analyzed old aerial photographs while searching for unexploded ordnance dropped by Allied aircraft over Germany's industrial Ruhr region.

While unexploded WWII-era bombs are regularly discovered in Germany, they are rarely as big as this one.

A similar bomb find two years ago prompted the evacuation of some 45,000 people in the city of Koblenz along the Rhine river.