ATHENS, Greece— On Sunday, a stationmaster who is suspected of being responsible for Greece's deadliest train accident was charged with negligent homicide and imprisoned pending trial. Prime Minister Kyriakos Mitsotakis also expressed regret for any role the Greek government may have played in the tragedy.

The railway employee should be charged with multiple counts of homicide, as well as charges of causing bodily harm and endangering transportation safety, according to the prosecutor and the examining magistrate.

A northbound passenger train and a southbound freight train collided late Tuesday north of the city of Larissa in central Greece, killing at least 57 people, many of them in their teens and 20s.

The two trains, which were headed in different directions, were allegedly directed onto the same track by the 59-year-old stationmaster. Before being charged and ordered held, he testified about the circumstances leading up to the crash for 7 and a half hours on Sunday.

The stationmaster's attorney, Stephanos Pantzartzidis, told reporters that his client gave an honest deposition without worrying about being implicated. Given the significance of the case, "the decision (to imprison him) was expected."

Insinuating that judges should look into whether more than one stationmaster was required to be on duty in Larissa at the time of the collision, Pantzartzidis suggested that parties other than his client share responsibility.

He was in charge of (train) safety in all of central Greece for 20 minutes, according to the client's attorney.

The stationmaster's error was made possible, according to Greek media reports, by a malfunctioning automated signalling system in the crash site. Stationmasters use two-way radios to communicate with one another and train drivers while manually operating the switches along that section of Greece's main trunk line.

The new Greek transportation minister would announce a safety improvement plan, the prime minister promised, and an immediate investigation into the collision would be conducted. A commission will be established to look into the nation's railway system's decades-long mismanagement once a new parliament is in place, Mitsotakis said.

Greece's railways have experienced long-term poor management, including extravagant spending on projects that were ultimately delayed or abandoned. Maintenance work was postponed because Hellenic Railways, a state-owned railroad company, was billions of euros in debt.

According to Panayotis Paraskevopoulos, a retired railway union official, the signalling system in the region under the stationmaster's supervision in Larissa malfunctioned six years ago and was never fixed.

Police or prosecutors have not identified the stationmaster, but his name was made public in a statement suspending the company inspector who selected him.

The 59-year-old stationmaster was transferred to a Ministry of Education desk job in 2011 when Greece’s creditors demanded reductions in the number of public employees but were transferred back to the railroad company in the middle of 2022 and enrolled in a five-month stationmaster training program.

He was assigned to Larissa on January 23 after finishing the course, but he rotated to other stations for the following month before going back to Larissa in late February. 12,000 people attended a protest rally that the railway unions organized on Sunday in the heart of Athens.

When 200 masked, black-clad individuals started throwing marbles, rocks, bottles, and firebombs at officers, five people were detained and seven police officers were hurt.

Two protest gatherings were attended by about 3,000 people in Thessaloniki. Aristotle University, the largest university in Greece with more than 50,000 students, is located in the city and was home to several crash victims.

A larger demonstration led by left-leaning activists marched to a government structure. There were no reported incidents at that gathering.

In the other, which was organized by members of the Communist Party and took place at the White Tower, the city's emblematic monument, there was a brief altercation with police when the protesters attempted to hang a banner on the monument.

"The Communist Party organized a symbolic protest today in front of the White Tower to denounce the crime in Tempe because it is a premeditated crime, a crime committed by the company and the bourgeois state that supports these companies," said Giannis Delis, a communist lawmaker.