A Greek rail inspector was detained on Friday, a court official said, as authorities investigate last month’s head-on train collision that killed 57 people and shocked the country. Identified as 63-year-old Dimitris Nikolaou, he was on duty at the time of the accident on February 28, when a passenger train and a freight train rammed into each other. The inspector, who was charged with the crime of negligent homicide and endangering public transport, is the second rail worker to be detained in the probe of Greece’s deadliest train disaster. The stationmaster on duty near the site of the crash has also been charged and jailed, after admitting to being partially responsible for the crash. Two other rail employees were taken in for questioning and charged in connection with the disaster but were released on bail earlier this week. The collision occurred after the trains ran along the main railway line between Athens and Thessaloniki, in the Tempe Valley of Thessaly, central Greece, without any alarms being sounded. Over 350 people were on board the two trains, including dozens of students returning to Thessaloniki after a long Carnival weekend.