Human error by a train controller was to blame for a crash in Bavaria, Germany, last week that killed 11 people, prosecutors said.
More than 80 people were injured after two commuter trains collided on a single-track stretch of railway.
An area controller opened the track to the two trains and tried to warn the drivers, according to the prosecutors.
The man, a 39-year-old, is likely to be charged with involuntary manslaughter and could face five years in jail.
“If he had complied with the rules… there would have been no collision,” said Chief Prosecutor Wolfgang Giese.
The trains crashed head-on while both were travelling at about 100km/h (60mph) east of Bad Aibling, a spa town about 60km south-east of Munich.
Investigations focused on why the trains were on the tracks at the same time despite safety mechanisms.
The crash site is on a bend, meaning the drivers no visual contact so collided largely without braking, officials said.
Prosecutors said the controller’s actions had catastrophic consequences but they do not believe he acted deliberately.
All those killed in the crash were men aged between 24 and 59.