By AYE NAI Derek Mitchell, the U.S. special envoy to Burma, talks to reporters at a news conference at Yangon International Airport September 14, 2011. (Reuters) US special envoy to Burma Derek Mitchell paid an official visit to Mandalay last Friday during a fact finding mission to ensure that April’s by-elections will be free and fair, amid reports that voting has been scrapped in 10 villages in Kachin state.