CNN– Rescue workers are searching for survivors after a head-on collision between two trains in central Greece killed dozens of people and left scores injured, raising questions about the country’s poor track record of railway safety.

At least 36 people were killed when a passenger train carrying more than 350 people collided with a freight train on Tuesday, shortly before midnight, in Tempi, near the city of Larissa, leaving strewn carriages and heaps of debris in its wake. The Greek Fire Service said 66 people were being treated for their injuries in hospital, with six in intensive care units.

The country’s transport minister resigned Wednesday, saying the railway system the government inherited was “not up to 21st century standards.”

The two trains involved in the fatal collision were traveling on the same track for many kilometers before the incident occurred, state-owned public broadcaster ERT reported Wednesday. The passenger train had changed lanes and switched to a cargo track before it collided head-on with a freight train, according to ERT.

Recovery efforts are underway, with the focus on the first carriages of the passenger train, the Greek Fire Service said. The death toll is expected to rise.

Images on ERT showed plumes of thick smoke pouring out of toppled carriages and long lines of rescue vehicles next to them.

Most of the passengers involved in the accident were young, the head of the intensive care unit (ICU) at a local hospital where those with injuries are being treated, told ERT Wednesday.

The process of identifying victims has also begun, Greek Health Minister Thanos Plevris said.

‘Not up to 21st century standards’

The deadly crash raised questions about the integrity of railway infrastructure in Greece.

Greece has a weak record of railway passenger safety compared with other countries in Europe, tallying the highest railway fatality rate per million train kilometers from 2018 to 2020 among 28 nations on the continent, according to a 2022 report from the European Union Agency for Railways.

“It is a fact that we received the Greek railway system in a state that is not up to 21st century standards,” Greek transport minister Kostas Karamanlis said Wednesday as he resigned, adding that in the last three-and-a-half years the government had “made every effort to improve this reality.”

“Unfortunately, our efforts have not been sufficient to prevent such a bad incident. And this is very heavy for all of us and me personally.

“I hand in my resignation as transport and infrastructure minister. It is what I feel is my responsibility to do as the minimum sign of respect to the memory of the people who died so unjustly.”

During a visit to the site on Wednesday, Greek Prime Minister Kyriakos Mitsotakis vowed to find out what caused the collision.

“It is very difficult what we are experiencing today as a country. We are talking about an unspeakable tragedy,” Mitsotakis told reporters.

“One thing I can guarantee: We will find out the causes of this tragedy and do everything in our power to make sure this never happens again.”

Greek police told CNN that they had arrested the station manager of a train station in Larissa on Wednesday as part of a preliminary investigation. A 59-year-old man is being held in the city and is expected to appear before the prosecutor, Greek police spokeswoman Constantia Dimoglidou said Wednesday.

‘Fire was right and left’

Passengers scrambled to escape the wreckage of the collision, as photos emerged showing the devastation of the crash.

“I walked forward and saw the worst part of the collision. The whole train had bent 90 degrees, had fallen over the cliff and half was in the air hanging and the whole thing was on fire,” a commuter told Skai TV, per CNN affiliate CNN Greece.

“There was panic … the fire was immediate, as we were turning over we were being burned, fire was right and left,” said 28-year-old Stergios Minenis, according to Reuters.

“We just heard a bang… the (train) car started spinning, before ending up sideways when we managed to exit,” another male passenger told Greek public broadcaster ERT.

“It was 10 nightmarish seconds with fire, you couldn’t see much from the smoke,” said a second passenger.

The passenger train had been traveling from the capital Athens to Thessaloniki, Greece’s second-largest city, which is renowned for its festivals and vibrant cultural life. The collision follows a nationwide carnival at the weekend which ended with a public holiday on Monday.

Greek Fire Service spokesman Vassilis Varthakogiannis said earlier that 194 passengers had been taken safely to Thessaloniki and 20 people transferred by bus to the city of Larissa.

At least 150 firefighters including special rescue units with 17 vehicles and 30 ambulances were involved in the rescue operation, Varthakogiannis added.

The Greek railway company, Hellenic Train, said in a press release that there was “a head-on collision between two trains: a freight train and train IC 62 which had departed from Athens to Thessaloniki.”

Hellenic Train, the main Greek railway company, was acquired by Ferrovie dello Stato Italiane in 2017 and is now fully controlled by Trenitalia. The company operates both passenger and freight transport. The main line on which daily connections are offered is Athens-Thessaloniki.

Condolences poured in from across the world, as Greek government officials declared a three-day mourning period with flag at half-staff starting Wednesday.

CNN’s Allegra Goodwin, Yusuf Gezer and Joseph Ataman contributed reporting.