As the Securities and Exchange Committee (SEC) continues its lengthy, convoluted investigation into the causes of the messy financial crisis, it is turning its attention to credit-rating firms, against which it may soon bring civil fraud charges.

Yesterday the McGraw-Hill Cos. announced that it had received notification that the SEC is considering bringing a civil action against the company’s Standard & Poor’s Ratings Services (S&P) unit. The action alleges that S&P’s ratings for a collateralized debt obligation violated securities laws.

The announcement comes nearly four months after the SEC unanimously voted to create more stringent regulations for credit-ratings firms that would require firms to disclose more information about credit ratings and what methodologies were used to determine them.