Four people were injured near a bridge near Munich's busy main train station on Wednesday, after an old aircraft bomb exploded.
Police say the explosion happened as the site was being drilled to build a tunnel.
The blast resulted in rail travel to and from the main train station being suspended.
World War Two bombs are often discovered during construction work in Germany, and are usually defused by experts or destroyed in controlled explosions.
In fact, more than 2-thousand tons of live bombs and munitions are discovered each year, more than 70 years after the end of the second World War.
This comes as British and American warplanes devastated the country with 1.5 million tons of bombs, with officials estimating 15-percent of the bombs having failed to explode, some of which were buried six meters deep in the ground.
Germany has previously reported deadly explosion due to the buried bombs, including in 2014 when a construction worker was killed when his power shovel struck a buried bomb.