OMAHA, Neb. (TheStreet) -- Berkshire Hathaway (BRK.A) Chairman and CEO Warren Buffett Saturday said former lieutenant David Sokol clearly violated Berkshire's ethical standards.

Speaking at his company's annual meeting, Buffett said he doesn't think he will ever understand why Sokol bought shares in Lubrizol ( LZ) before recommending that Berkshire buy the company, according to an Associated Press report.

The so-called Oracle of Omaha said he made a mistake by not asking Sokol more about his Lubrizol holdings when the two first discussed the company in January, the report said.

But Buffett added that he didn't have any reason to think that Sokol had just purchased his Lubrizol shares, according to the report.

Sokol, who had been considered an heir apparent to the 80-year-old Buffett, has denied any wrongdoing but left Berkshire earlier this month.

In advance of the meeting, observers had been hoping Buffett, who has often been held up as a model of ethical management, would address the issue of Sokol's Lubrizol purchases.

Berkshire Hathaway Chairman and CEO Warren Buffett tours the exhibit floor before presiding over the annual Berkshire Hathaway shareholders meeting Saturday.

Buffett said he wasn't more critical of Sokol when he announced his lieutenant's resignation in March because he didn't have all of the information about the issue at the time, the AP report said.

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Also Saturday, Berkshire issued preliminary first-quarter results, saying losses in its insurance underwriting businesses helped cause earnings to fall to $1.51 billion from $3.63 billion a year earlier.

Berkshire's Class A shares ended Friday down $55 at $124,750. The company's Class B stock finished the session up 3 cents at $83.30.

This article was written by a staff member of TheStreet.