The Greek police force has ordered an internal investigation to determine how a 25-year-old foreign national escaped from a detention center on Saturday even though four officers had been appointed to supervise him. The suspect, a convict on drug charges who had been awaiting his appeal hearing, managed to escape the detention unit in Fthiotida, central Greece, and board a train to Athens. Police eventually traced him later on Saturday and he is back in detention. But police chiefs are concerned at how the suspect managed to escape as four police officers had been on duty at his unit. The incident comes just a few weeks after a 30-year-old man arrested for petty theft in Thessaloniki jumped out of a police patrol car, hijacked several cars and shot dead a bus driver. The suspect grabbed the unattended weapon of one of the two officers in the car.