The Financial Post reports in its Saturday, Sept. 20, edition that Magna International said Friday that Brazil's competition regulator had visited the offices of its Brazilian subsidiary in connection with an antitrust investigation. A Reuters dispatch to the Post reports that Magna offered no details on the focus of the investigation. The auto parts supplier said it would co-operate with the authority, the Conselho Administrativo de Defesa Economica. Magna shares tumbled $5.71 to close Friday on the Toronto Stock Exchange at $113.33. Despite Friday's share slide, Magna's equity is up 33 per cent so far this year. Magna does not break out how much of its $35-billion in annual revenue comes from Brazil. Magna has said South America is its "most substantial market" outside of North America and Europe. That segment accounted for $2.57-billion in sales last year. Magna has 10 factories and 3,725 employees in Brazil, where its Cosma International unit operates. Magna said in its second quarter earnings release that it continues "to focus on reducing operating losses and addressing commercial challenges in South America." The stock was trading at $123.36 on Sept. 2.