Several people were injured in the explosion of an aircraft bomb from World War II on Wednesday in Munich.
The detonation occurred on a Deutsche Bahn construction site near the Donnersbergerbrücke, the police said.
One person was seriously injured, two others were slightly injured.
Experts from the ordnance disposal service were involved in the investigation.
Interior Minister Joachim Herrmann (CSU) was at the scene of the accident at noon to get an idea of the situation.
An aerial bomb weighing 250 kilograms was hit during drilling, said Herrmann, who wished the injured a good recovery.
Why the bomb was not discovered in advance is still unclear.
Normally, during construction work in downtown Munich, it is always carefully and regularly probed where duds could be.
Rail traffic around Munich Central Station has been discontinued.
That affects long-distance and local transport, said a rail spokesman.
How long the traffic would stand still was initially unclear.
The police and fire brigade went on a large-scale operation.
According to the police, there was a loud bang, then a column of smoke formed.
The fire department spoke of an explosion.
"We are in the process of taking care of the people," said a fire department spokesman on site.
The Donnersbergerbrücke is not far from the main train station in the center of Munich on the main route of the Munich S-Bahn.
Numerous fire engines and around 50 emergency services were on site, a federal police helicopter circled over the area.