An investigation into a wire-tapping scandal that targeted top government officials during the Athens 2004 Olympics was shelved yesterday by judicial authorities who said they had been unable to trace the culprits. Investigating magistrate Panayiotis Petropoulos had called for the case to be closed six months ago after failing to find any evidence of who had tapped the phones of Prime Minister Costas Karamanlis and dozens of others, including top-ranking politicians. A public prosecutor yesterday consented to shelve the probe. Some 500 witnesses were questioned in the period between February 2006, when the mobile operator Vodafone discovered that its system had been bugged, and last August when the investigation was suspended. Authorities last year fined the Greek branch of Vodafone 100 million euros for breaching privacy rules but the operator’s role in the affair was never clarified. Officials had claimed that Vodafone’s removal of the bugging devices, once they had been discovered, had made it impossible to trace the perpetrators.