Authorities have launched an investigation into an illegal pyramid scheme that allegedly earned an economics lecturer more than 15 million euros from more than 300 unsuspecting investors, some of whom included his students. Police said yesterday that Costas Christopoulos, of the Athens University of Economics and Business, is suspected of operating a business venture since 2000 that called for investment in exchange for high returns. Christopoulos offered his clients monthly returns of 3 to 5 percent, which mounted up to 60 percent per year. In order to qualify, investors were required to make bank deposits of between 10,000 and 30,000 euros in his personal bank account. Up until 2003, the lecturer was crediting his clients’ accounts with the promised returns but then stopped, offering the excuse that he was being audited by the tax office. The funds would then be laundered through a complex procedure involving a number of offshore companies, officers said. Police have launched a manhunt for Christopoulos.