But other big investors have been buying the beleaguered rating agency, whose shares have fallen 19% this year.

Berkshire , run by billionaire investor Warren Buffett, sold a million shares of the New York-based company in the first quarter ended March 31. Berkshire remains Moody’s biggest single investor with a 31 million-share stake worth $663 million at quarter-end.

Berkshire also sold some shares of Kraft , the food company with which Buffett, right, had a clash over how the firm sought to pay for its acquisition of the Cadbury candy giant. Berkshire cut its Kraft stake by almost a quarter, to 106 million shares.

With the latest round of sales, Berkshire has cut its Moody’s holdings by a third since last summer. The move comes at a time when the rating agencies are under fire for their role in the housing bubble and facing regulatory curbs on what was their fastest-growing business.

The timing of some of Berkshire’s sales has raised some eyebrows in some quarters. Berkshire sold shares the day Moody’s received notice from the Securities and Exchange Commission that it could face an enforcement action over its failure to enforce its rating policies.

But Berkshire, which has held shares of Moody’s and its predecessor company for more than a decade, has been paring back with some regularity for the past year (see chart below).

Despite the headaches, Buffett said at Berkshire’s annual meeting this month that he believes Moody’s and its rival Standard & Poor’s have “incredibly wonderful businesses,” thanks to the continuing lack of competition. Wall Street analysts estimate that Moody’s and S&P, a unit of McGraw-Hill (MHP), control 95% of the business of rating securitized bonds, for instance.

It seems that many big holders of Moody’s stock are following Buffett’s words rather than his deeds. Three of the firm’s top 10 shareholders added to their positions in the first quarter, according to data compiled by Lionshares.com.

Capital World Investors, the third-biggest Moody’s holder with a 10% stake, bought 4.7 million shares in the latest quarter. No. 4 shareholder Fidelity, which holds 9% of Moody’s, added a million shares. The biggest buyer, though, was No. 10 investor Invesco, which bought almost all its 6 million shares during the period.

Moody’s shares rose 2% in trading Tuesday to $21.85.