Shares of Six Flags, the world's second-largest theme-park operator behind Disney, rose 8.6 percent to $7.10 in early trading on the New York Stock Exchange. At that price, the company's market capitalization is roughly $661 million.
Six Flags said it would invite dissident shareholder Red Zone LLC — an investment firm controlled by Snyder — to participate in the auction. But it also said it opposed Snyder's attempt to gain control of the company through a tender offer for Six Flags stock.
Last Thursday, Red Zone said in a letter to shareholders it sought to boost its stake to 34.9 percent from a current 11.7 percent, and would offer $6.50 per share — valuing the entire company at about $605.2 million. However, the tender offer is contingent upon the replacement of Burke and Chief Financial Officer James Dannhauser.
Details of the auction were not spelled out. Six Flags did not offer a timetable, saying only that it would be thorough and prompt.
Karl Swanson, a spokesman for Snyder, said Red Zone was waiting for more information.
"We haven't received any details of the auction," Swanson said. "We'll be happy to see just how they intend to do it."