Two people were slightly injured when a German regional train near Stuttgart began to smoke after making an emergency stop.
The injured were treated on the spot by emergency services, a spokesman for the federal police said on Saturday.
An overhead line was also damaged in the incident, which took place not far from the town of Plochingen.
The reason for the emergency braking manoeuvre on Friday evening was initially unclear, but according to the police on Saturday, human error is assumed. In order to clarify the exact cause, evidence is being secured and witnesses are being questioned, police said.
The 300 or so passengers on the train were evacuated.
The amount of damage caused to the train and the overhead line is still being determined.