THESSALONIKI, Greece — Three more Greek rail officials were charged on Thursday in connection with a train crash that killed 57 people, as protests continued and the government promised to overhaul rail safety.

Two station managers and a supervisor were charged with endangering rail safety leading to the loss of life, a senior official involved in the investigation told the Associated Press on condition of anonymity, citing judicial policy. The three have been summoned to provide additional testimony and have not been detained.

The charges are similar to those filed against a 59-year-old station manager who was arrested in the wake of the Feb. 28 crash in northern Greece and is currently in pre-trial detention.

Protests in Athens and other cities continued Thursday, following large rallies and strikes nationwide a day earlier to protest the government’s response to the head-on collision along Greece’s main rail route, outside the northern town of Tempe.

The disaster involving a passenger train and a freight carrier has set back widely reported plans by Greece’s center-right government to call a general election for early April.

Prime Minister Kyriakos Mitsotakis must hold elections before July. He vowed Thursday to press ahead with immediate and longer-term safety improvements that include higher staffing levels and stricter staff supervision along the rail network.

He repeated a public apology for the crash but added that previous governments also shared responsibility for long-term failings regarding rail safety.

“I take responsibility. We can’t — we don’t want to, and we should not — hide behind a series of human errors,” he told a televised meeting of Cabinet ministers.

Popi Tsapanidou, a spokesperson for the main left-wing opposition party, Syriza, called the apology insincere. “Mr. Mitsotakis should realize that he did not become prime minister the day before yesterday,” she said. “He has been governing for the past four years.”