Billionaire investor Nelson Peltz bought 12.2 million shares in Kraft Foods during the first quarter, his investment firm reported this week.

Based on yesterday’s close of $34.53, the new stake would be worth about $421.3 million — or about two-thirds of 1 percent of Kraft shares.

A spokeswoman for Peltz did not respond to a request for comment.

Peltz holds the stake through his Trian Fund Management, which did not report the stake when it made its regular quarterly filing.

Peltz previously owned a stake in Kraft, the maker of Oreo cookies, Oscar Mayer meats and other foods, and named two board members as part of a deal with the Northfield, Ill., company.

“We are aware of the disclosure of Trian’s investment,” a Kraft spokesman said in an e-mailed statement. “We welcome all shareholders that invest in Kraft Foods. As always, we’ll continue to manage the business for the benefit of all shareholders.”