Warren Buffett's Berkshire Hathaway Inc. stands to make at least $680 million in profit from a 2008 investment in candy company Mars Inc.

Mars recently bought back $4.4 billion of bonds from Berkshire that it had sold to the giant conglomerate to help finance a $23 billion purchase of Wm. Wrigley Jr. Co., people familiar with the matter said.

Berkshire sold the notes back at 115.45% of their face value as well as accrued interest on Oct. 1, one person said.

"We can confirm that on October 1st, 2013 we repaid $4.4 billion of subordinated notes lent to Wrigley by Berkshire Hathaway. Berkshire Hathaway status as minority owner of Wrigley remains unaffected," a Mars spokesman said.

Berkshire continues to own $2.1 billion of preferred stock in Wrigley, which operates as a wholly-owned subsidiary of Mars.