Police officer Christoph Schulte said the incident appears to have started inside the station.
He said parts of the station, one of the biggest in the country, were closed off as well as Breslauer Platz square behind the station.
There were no immediate details on who was taken hostage or how many people were involved.
German railroad operator Deutsche Bahn tweeted that some of the station’s tracks were shut down temporarily.
Police on Twitter told people to avoid the station.