Investigators into the collapse of the Italian dairy giant Parmalat are turning the spotlight on America's big investment banks. Italian magistrates and officials from the powerful Securities and Exchange Commission are examining the role of lenders to Parmalat - which collapsed into administration last month following the disclosure of an €8 billion (£5.6bn) hole in its finances. These lenders include some of the US's largest financial institutions. An SEC source said that while at this stage an investigation did not imply wrongdoing by the investment banks, it was focusing on placements of notes and bonds in the US. But he...