Four people were injured when an old aircraft bomb exploded at a bridge near Munich's busy main train station on Wednesday, police said on Twitter, raising the number of wounded from three earlier.
The Munich fire brigade said one of the people was seriously injured, Reuters reported.
The explosion happened as the site was being drilled to build a tunnel, police said, adding the area had been cordoned off. "There is no danger outside this area," police said.
Explosives experts were summoned to the site to examine the remains of the bomb, the fire brigade said.
Due to the blast, rail travel to and from the main train station was suspended, according to rail operator Deutsche Bahn.
More than 2,000 tonnes of live bombs and munitions are discovered each year in Germany, more than 70 years after the end of World War Two.
British and American warplanes pummelled the country with 1.5 million tonnes of bombs that killed 600,000 people. Officials estimate that 15% of the bombs failed to explode, some of which were buried six meters deep in the ground.
