German investigators on Wednesday were working to determine what caused the collision between a passenger train and a stationary freight train near the city of Duesseldorf that injured 41 people.
Early indications suggested the passenger train had been on the wrong track, but officials said it remained unclear how the mistake could have happened.
Seven of the 41 hurt were badly injured in Tuesday's accident, while one person was in a serious condition, the local Meerbusch fire department said in an updated toll.
A total of 173 people were on board the National Express regional train when it smashed into a DB Cargo train around 7:30 pm (1830 GMT) near Meerbusch-Osterath station in North Rhine-Westphalia, Germany's most populous state.
Rescue workers and officials praised the driver for slamming on the emergency brake as soon as he noticed an obstacle on the tracks, likely preventing a much bigger collision.
"We were very lucky," said spokesman Marcel Winter of Britain's National Express. "It could have been much worse."
The driver was unharmed but in a state of shock, police said.
Images from the Tuesday's late night scene showed moderate damage to the passenger train's first carriage, while the other blue-and-white carriages appeared largely unaffected.
The train remained standing upright on the tracks.
Some of the cargo train carriages however were thrown off the rails as a result of the impact.
"The regional train should not have been on that section of the track," said Gerd Muennich, a spokesman for the Federal Railway Accident Investigation Board (BEU).
The cargo train had been standing still waiting for a signal to proceed, he added, while declining to speculate on whether the crash was caused by human error or a technical problem.
"We are only at the very beginning of our investigation," he stressed.
- 'No panic' -
Passengers recounted hearing a loud bang when the two trains collided but 19-year-old Lukas Kehler said people remained calm.
"There was no sense of panic," he told local television station WDR.
The crash sparked a large rescue operation involving some 400 emergency workers but access to the train was initially hindered by ruptured overhead lines which first had to be made safe, according to the Meerbusch fire department.
Rescuers were able to reach those injured by 9:15 pm (2015 GMT), with the last people evacuated from the train just after midnight.
The regional express train was travelling from the western city Cologne to the town of Krefeld while the cargo train was bound for the Dutch city of Rotterdam.
National Express is the only private rail operator active in North Rhine-Westphalia, where it has been running two regional services since 2015.
Germany's deadliest train accident happened in 1998 when a high speed train operated by state-owned Deutsche Bahn derailed in Eschede in Lower Saxony, killing 101 people.