STORY: Police fired tear gas at rock-throwing protesters who lit fires in the streets. Earlier a candlelit vigil was held outside the offices.
A Greek passenger train collided head-on with a cargo train late on Tuesday near the northern city of Larissa, throwing entire carriages off the tracks and killing at least 38 people, many of them students, in the country's deadliest rail crash in living memory.
Officials said the death toll was expected to rise further as temperatures in one carriage rose to 1,300 Celsius after it was engulfed in flames.
The local station master, in charge of signaling, has been arrested and charged with causing mass deaths and grievous bodily harm through negligence, a police official said.
The 59-year-old man has denied any responsibility for the accident, attributing it to a possible technical failure, the official said.