A Greek stationmaster is set to appear Thursday before a prosecutor as the country mourns following the collision between a passenger train and a freight train that killed at least 43 people and injured 85 more.

The collision occurred late Tuesday near the city of Tempe, about 380 kilometers north of Athens, the Greek capital.

Prime Minister Kyriakos Mitsotakis said in a televised address Wednesday after visiting the crash site that it appeared the cause was a “tragic human error.” He promised a full investigation.

Transportation Minister Kostas Karamanlis resigned Wednesday, accepting responsibility for the accident.

Karamanlis said the Greek railway system was “not up to 21st century standards” when he took office. “In these 3.5 years we have made every effort to improve this reality,” he said. “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.”

He said resigning was “the minimum sign of respect to the memory of the people who died so unjustly.”

The government declared three days of mourning beginning Wednesday, while in Brussels, flags were lowered to half-staff outside buildings of the European Union.

The cargo train was traveling south from Thessaloniki to Larissa with a crew of two, while the other train, with about 350 passengers, was headed north from Athens to Thessaloniki.

Yiannis Ditsas, head of the Greek rail workers’ union, told Greek television that the two trains barreled toward one another for 12 minutes before colliding. At least three passenger cars derailed and burst into flames.

By Wednesday morning, authorities reported that at least 66 of those injured were still hospitalized, with six of them in intensive care.

Rescue workers continued to search through the crash site, where an overturned blue passenger carriage remained in an open field. Other carriages were flattened.

Before his resignation, Karamanlis said, “It’s a difficult search and rescue operation and we still don’t know the exact number of victims. We will investigate with full seriousness and with full transparency the causes of this tragic incident.”

Greece’s health minister, Thanos Plevris, said many of the passengers on the northbound train were college students and other young people. Greek media reported that many of them had been returning from carnival celebrations in Athens.

Authorities say about 250 passengers who survived the crash unharmed or with minor injuries were transported by bus to Thessaloniki.

Greece has struggled with rail safety in recent years, with the EU saying the country had the highest railway fatality rate per kilometer traveled in the 27-nation bloc between 2018 and 2020.

Some information for this report came from the Associated Press, Agence France-Presse and Reuters.