Over the past decade, Amado Yáñez Osuna gained a reputation throughout Mexico as a highflying CEO with good political ties. He turned up at events with prominent ruling-party members, and lent his private jet to party officials. But then the party lost power. On Thursday, officials arrested Mr. Yáñez and charged him with violating banking laws. Authorities say his company, oil services firm Oceanografía, defrauded Banamex, the Mexican unit of U.S. banking giant Citigroup , of about $400 million. Citigroup has already fired 12 employees in Mexico for failing to detect the alleged fraud, which was tied to alleged fake documents from state-owned oil firm Petróleos Mexicanos, or Pemex. The arrest deepens a scandal that has sent shock waves across Mexico’s political landscape. That […]