Police probe door opening on German train travelling at 200 km/h

A door on a German high-speed ICE train carrying 238 passengers opened while the train was travelling at around 200 kilometres per hour, prompting a major emergency operation, police said on Wednesday.

The driver immediately stopped the Munich-to-Dortmund train near the entrance to a tunnel at Karlstadt in the southern state of Bavaria on Tuesday evening. No one was injured.

Rail operator Deutsche Bahn said there was no technical fault with the train, while federal police launched an investigation into how the door came to be open.

"Doors on ICE trains do not simply open while the train is moving," a company spokeswoman said, adding that the cause was now a matter for investigators.

Deutsche Bahn declined to comment on whether someone aboard the train could have deliberately opened the door.

As authorities initially could not rule out that someone had fallen from the train, federal and state police, firefighters and rescue services launched an extensive search of the tracks.

Drones, dog teams, a helicopter and thermal imaging equipment were deployed in the operation, which was complicated by darkness and rough terrain. No one was found.

Passengers were later able to leave the train in Lohr am Main, where federal police officers questioned them and recorded their identities.