Connecticut's attorney general is investigating possible conflicts of interest due to Berkshire Hathaway Inc's 20 percent ownership of credit ratings company Moody's Corp.

Berkshire, a holding company run by billionaire investor Warren Buffet, runs a newly created municipal bond insurance firm called Berkshire Hathaway Assurance Corp.

Attorney general Richard Blumenthal says his office is probing the clear and direct conflict of interest for Moody's to rate a company owned by such a significant Moody's shareholder, according to an interview with Bloomberg.

Blumenthal says the companies are cooperating with the investigation.

Class A shares of Berkshire Hathaway closed up 0.04 percent on Thursday, or $50.00, at $133,900 on the New York Stock Exchange. Moody's shares were up 4.41 percent, or $1.63, to close at $38.59.