Pension funds and insurance companies lost billions of dollars on securities that they believed were solid investments, according to former Goldman employees with direct knowledge of the deals who asked not to be identified because they have confidentiality agreements with the firm. Goldman was not the only firm that peddled these complex securities ... and then made financial bets against them, called selling short in Wall Street parlance. Others that created similar securities and then bet they would fail ... include Deutsche Bank and Morgan Stanley, as well as smaller firms like Tricadia Inc., an investment company whose parent firm was overseen by Lewis A. Sachs, who this year became a special counselor to Treasury Secretary Timothy F. Geithner. How these disastrously performing securities were devised is now the subject of scrutiny by investigators in Congress, at the Securities and Exchange Commission and at the Financial Industry Regulatory Authority. While the investigations are in the early phases, authorities appear to be looking at whether securities laws or rules of fair dealing were violated by firms that created and sold these mortgage-linked debt instruments and then bet against the clients who purchased them, people briefed on the matter say.