"I didn't think Warren would be interested in buying Lubrizol anyway," Fox Business Network cited Sokol as saying in an interview. "The only reason Warren Buffett mentioned it in the release is because it would have to be brought up anyway when Berkshire put the purchase up for a vote."

Ann Thelen and Tina Potthoff, spokeswomen for MidAmerican, didn't return calls and e-mails seeking comment from Sokol. Debbie Bosanek, an assistant to Buffett, confirmed his statement.

A surge in options trading in the week before the takeover suggests that investors may have been speculating with insider information, according to Ophir Gottlieb, head of client services at Livevol Inc., a San Francisco-based provider of options-market analytics. Call trading surged to 2,931 contracts on March 9, and open interest for the April $110 calls jumped to 2,654 from 41.

Scouting Acquisitions

Sokol joined Omaha, Neb.-based Berkshire in 2000 when he sold MidAmerican, which he led as CEO, to Buffett for about $9 billion. Under Berkshire, Sokol retained a minority equity stake in MidAmerican and expanded the unit by buying a natural gas pipeline and power producers in California and the U.K.

Sokol relinquished the CEO job in 2008 and broadened his duties at Berkshire by scouting deals like an investment in China's BYD Co. and a rescue for Constellation Energy Group Inc.

"He was the heir apparent," said David Kass, a professor at the University of Maryland's Robert H. Smith School of Business. "The exercise of his recommending Lubrizol to Warren Buffett was like a CEO in training."

Sokol instructed Citigroup Inc. on Dec. 13 to arrange a meeting with Lubrizol CEO James Hambrick, according to an SEC filing last week. The two men spoke on the telephone on Jan. 14 and met on Jan. 25. Sokol told Buffett he was a shareholder in Lubrizol, the Wickliffe, Ohio-based maker of engine lubricants, when the two men first discussed a possible deal, according to the statement yesterday.

'Passing Remark'

"It was a passing remark and I did not ask him about the date of his purchase or the extent of his holdings," Buffett said. Buffett learned about the size and dates of the purchases "shortly before I left for Asia on March 19," he said.

Sokol's stake as reported by Buffett would have been worth about $9.92 million on Jan. 7, based on the closing price on the New York Stock Exchange. The shares have risen about 30% to $134.01 since Buffett's deal was announced, boosting the stake, if Sokol still owns it, to $12.9 million.

"I don't attribute this to a failure of character or a scheme, but rather more of an honest oversight that happens in the hustle and the bustle of trying to get jobs done and the enthusiasm that comes about from a good idea," Thomas Russo, a partner at Berkshire investor Gardner Russo & Gardner, said of Sokol's trades. "There's way too much at stake to risk for such small reward."

'Totally Honorable'