A Thessaloniki prosecutor has ordered a preliminary investigation into how a student was arrested last Sunday for possessing a petrol bomb only to be freed later when video and photographic evidence emerged appearing to show officers placing a bag containing a petrol bomb that did not belong to the 24-year-old next to him. The student protested his innocence in court, saying he had come down from his apartment in his pyjamas to throw rubbish into a dumpster when he was caught up in rioting in the northern city. The suspect used the video evidence to back up his claims that the bag with the Molotov cocktail had been planted on him. The 24-year-old was released on the strength of the video and photographs of the arrest. The police apologized and said its officers would be investigated but prosecutor Dimitris Papageorgiou has launched a separate probe into the affair.