(Reuters) - Pinnacle Foods Inc, the U.S. food company that went public on Thursday, is looking to add more brands to a portfolio that already includes Birds Eye vegetables, Vlasic pickles and Duncan Hines cake mixes, its chief executive said.

"We're interested in more M&A," CEO Bob Gamgort told Reuters. "We're very active in proactively identifying M&A, which is the right way to do it. We see that as an upside and we're interested in making that happen, but obviously we don't control it."

Gamgort, who joined Pinnacle from Mars Inc, said the company's first priority would be to expand its position in current or adjacent categories, such as frozen foods, where it also owns Mrs. Paul's seafood. The company is not interested in expanding beyond North America or into other "temperature classes" like refrigerated or fresh foods, he said.

Shares of the Blackstone Group LP backed company were up 13.7 percent from its IPO price at $22.73 on Thursday, after it raised $580 million in its initial public offering. (Reporting By Martinne Geller in New York; Editing by Gerald E. McCormick)