That's what U.S. authorities will want to know. Wal-Mart's shareholders will be asking the same question," he said. A spokesman at the SEC said it did not have any comment on the New York Times article. A Justice Department spokeswoman declined to comment. Wal-Mart de Mexico, or Walmex, as the company is known locally, has expanded rapidly since Walmart opened its first store outside the United States in Mexico City in 1991, then part of a joint venture. In 2011, the Mexican unit reported total sales of 379 billion pesos ($29 billion). Walmart's fiscal 2012 sales, for the year ended Jan. 31, were $443.85 billion. STEPS TO CONCEAL PAYMENTS Middlemen or "gestores" are used in Mexico to help companies perform a variety of tasks, from obtaining residency permits and resolving tax issues to obtaining planning authorization.