Mexican billionaire Carlos Slim started buying Citigroup shares last week through his investment vehicle Inbursa, according to a CNBC report.  Inbursa has bought roughly 26 million shares of Citi.

Some analysts have speculated that Citigroup could decide to sell its Banamex bank in Mexico to raise capital for its U.S. operations.  If Banamex is put up for sale, Slim could be a buyer.