(Bloomberg) -- A multi-billion-dollar gold project owned by the world’s biggest bullion producer has been invaded by illegal diggers in northern Peru, according to a top government official.   Newmont Corp.’s stalled Minas Conga project in the Cajamarca region “is being partially exploited by illegal mining,” Prime Minister Ernesto Alvarez told reporters Friday. Newmont didn’t immediately comment. Denver-based Newmont is the latest global company to face informal miners as near record prices increase incent ...