Police stand outside Cologne main railway station on October 15, 2018 in Cologne, Germany.
Michael Gottschalk | Getty Images
The main train station in the western German city of Cologne has been closed due to an ongoing police operation, state-owned rail operator Deutsche Bahn said on Monday after police said they were investigating a suspected hostage-taking.
"A police operation is delaying rail traffic, the main station in Cologne is closed," Deutsche Bahn said on Twitter, adding it did not know how long the police operation would last.