Greece was looking for answers as the toll from the deadly train crash near Larissa climbed to 42, the fire department said Thursday.

A fire department spokeswoman told AFP that rescue crews had worked all night in search of survivors, but chances were dwindling. "Time is not on our side," she said.

The accident took place late Tuesday when two trains collided near a tunnel outside Larissa. Two carriages were crushed and a third caught fire, trapping people inside.

Passengers have described scenes of horror and chaos from the crash, many dodging smashed glass and debris as the train keeled over, and breaking windows to climb out.

Rescuers at the scene said they had never dealt with a disaster of this magnitude before.

Many bodies were charred beyond recognition and some passengers were being identified from body parts.

Several people are still believed to be missing – including two Greek Cypriots – though authorities have not released an official estimate.

The station master on duty at the time of the accident was due to appear before a prosecutor at the central city of Larissa later Thursday.

The 59-year-old will have to explain how a passenger train carrying some 350 people was allowed to run on the same line as a freight train for several kilometers.

"It was a student train, full of kids...in their 20s," Costas Bargiotas, a senior orthopedic doctor at Larissa General Hospital, told Skai TV.

"It was truly shocking... the carriages crumpled like paper," he said.

Prime Minister Kyriakos Mitsotakis – who will seek re-election this year with ballots expected in April – said it was a "terrible train accident without precedent" in Greece, promising that the tragedy would be "fully" investigated.

'Tragic human error'

"Everything shows that the drama was, sadly, mainly due to a tragic human error," Mitsotakis said in a televised address Wednesday after visiting the disaster site.

Authorities have declared three days of national mourning.

Passengers have described scenes of horror and chaos, dodging smashed glass and debris as the train keeled over, and forced to break windows to climb out.

"It was a nightmare ... I'm still shaking," 22-year-old passenger Angelos told AFP, adding that the collision felt "like a strong earthquake."

"It was the train of terror," Pavlos Aslanidis, whose son is among the missing along with a friend, told reporters.

Rescuers were forced to call off the search late on Wednesday to give exhausted crews and crane operators a respite.

Train unionists said the safety shortcomings of the Athens-Thessaloniki railway line had been known for years.

In an open letter last month, train staff said track safety systems were incomplete and poorly maintained.

A safety supervisor had resigned last year, warning that infrastructure upgrades, pending since 2016, were incomplete and that train speeds of up to 200 kilometers (124 miles) an hour were unsafe.

Five years after Greek rail operator Trainose was sold to Ferrovie Dello Stato Italiane and became Hellenic Train, safety systems on the Athens-Thessaloniki line are still not fully automated.

Students protest

Protests were held on Wednesday evening at the Thessaloniki train station, the city of Larissa and outside the Athens offices of the railway's Italian-owned operating company, Hellenic Train, where protesters threw rocks at the building and at police.

In Larissa, demonstrators held a silent vigil and brought white roses to form the word Tempe, the name of the valley where the accident took place.

Nikos Savva, a medical student from Cyprus, told AFP that the disaster was only a matter of time.

"The rail network looked problematic, with worn down, badly paid staff," he said.

The station operator will be charged with negligent homicide on Thursday and faces a life sentence if convicted.

But Savva said the man "should not pay the price for a whole ailing system."

"This is an inadmissible accident. We've known this situation for 30 years," Larissa doctor Bargiotas said.