Police raided the Larissa train station in Greece as part of the investigation into a collision between two trains that killed at least 57 people, a police spokesman said.
"The police have seized [...] all the documents which can help the investigation," the spokesman said, as anger mounts in Greece over the head-on crash Tuesday night.
A judicial source told AFP that audio files, documents and other evidence were among items seized.
The investigation is "aimed at initiating criminal proceedings, if necessary, against members of the company's management", she said, referring to the rail operator Hellenic Train.
The seized files "may help clarify the case and determine criminal responsibility", she said.
Police said 31 bodies have now been identified - almost all from DNA tests as the crash was so violent.
Hellenic Train was formed when the state-owned Greek rail operator Trainose was privatised five years ago and sold to Italy's Ferrovie Dello Stato Italiane.
The 59-year-old station master of Larissa station has been charged with negligent homicide.
His lawyer said his client has admitted partial responsibility for the crash, but emphasised that there were other factors at play in the accident.
Meanwhile Greek railway workers have extended their strike to a second day, and more protest rallies are planned, amid anger over a devastating train crash that killed at least 57, among them many university students.
Carriages were thrown off the tracks, crushed and engulfed in flames when a high-speed passenger train with more than 350 people on board collided head-on with a freight train late on Tuesday.
"The federation has been sounding alarm bells for so many years, but it has never been taken seriously," the main rail workers union said, demanding a meeting with the new transport minister, appointed after the crash with a mandate to ensure such a tragedy can never happen again.
The union said it wanted a clear timetable for the implementation of safety protocols.
Questions around the crash - which happened as the two trains were on the same track - involve faulty signalling and maintenance issues.
Work resumed at the crash site, where rescue staff used cranes to lift some of the carriages that were thrown off the tracks - which could be wrapped up today.
"The operation is under way, it was planned to end today, we hope it will end today but there's always the unknown factor," afire brigade official said.
It was unclear if more were still missing, or how many.
Amid shock and sorrow in a country where three days of national mourning have been declared, families and friends said they wanted answers over how such a crash could have happened.
Yesterday, outside the hospital in Larissa, where many of the victims were brought, a woman called Katerina, whose brother was missing, screamed: "Murderers! Murderers! I will leave tomorrow with a coffin!"
Katerina, whose anger was directed at the government and the rail company, had, like other relatives looking for loved ones, given a DNA sample to try and identify her brother.
A woman whose husband and five-year-old son were on the train told Greek TV: "All those people who are there, they're useless, useless. Some MPs are coming out and offering condolences, so what? Will it bring our children back?"
Asked if she gave DNA for identification, she said, on footage broadcast by Mega TV: "to identify what, ashes?"
After evening protests over the past two days, two more protest rallies are planned in Athens, around noon and in the evening.
