Leaders of indigenous communities in Ecuador are pressing their government to investigate senior executives from U.S. oil giant Chevron for an alleged environmental fraud scheme in the mid-1990s related to a long-running six-billion dollar class action suit in the South American nation. But the U.S. oil giant vehemently denies the accusations and says it has already been absolved by the local authorities....The indigenous people's letter [to the Quito government] claims that the [Chevron] officials' work severely underestimated the amount of toxins in the soil, with the aim of guaranteeing a legal release from future government claims. [also refers to Texaco (now part of Chevron), PetroEcuador]