"Swiss Steel Holding AG has been informed that BigPoint Holding AG has sold 306,000,000 shares of Swiss Steel Holding AG to PCS Holding AG," the firm said in a statement, corresponding to about a tenth of share capital and voting rights.

Through BigPoint, which previously held 51.4% of Swiss Steel, Haefner also controls automobile importer and dealer AMAG-Gruppe. Meanwhile, Frauenfeld-based PCS Holding is an investment company for Spuhler, who is also the chairman of trainmaker Stadler Rail.

Russian oligarch and billionaire Viktor Vekselberg's investment company Liwet is the other big owner in Swiss Steel, at nearly 17%, according to Refinitiv data.

Haefner and Vekselberg have been feuding over whether BigPoint should have to make a public tender offer for all of Swiss Steel, based on its ownership stake. In the latest decision in that case on Thursday, Swiss markets watchdog FINMA rejected an appeal by Liwet, though it can still fight that decision in Swiss court.

(Reporting by John Miller, Editing by Sherry Jacob-Phillips)