Three of the nation’s major credit rating agencies are the subject of a mortgage securities-related probe by New York’s top prosecutor, following the issuance of a subpoena and other requests for information on certain rated pre-financial crisis deals. New York Attorney General Eric Schneiderman quietly launched his own investigation last week into allegations that Standard & Poor’s, Moody’s Investors Service and Fitch Ratings issued favorable ratings to certain MBS leading up to the financial crisis to drum up more business. Schneiderman issued...