In 2009 the government of Mexico created a regulatory pathway for approval of genetically modified maize,[35] but because Mexico is the center of diversity for maize, concerns have been raised about the effect that genetically modified maize could have on local strains.[36][37] A 2001 report in Nature presented evidence that Bt maize was cross-breeding with unmodified maize in Mexico,[38] although the data in this paper was later described as originating from an artifact and Nature stated that "the evidence available is not sufficient to justify the publication of the original paper".[39] A subsequent large-scale study, in 2005, failed to find any evidence of contamination in Oaxaca.[40] However, other authors have stated that they also found evidence of cross-breeding between natural maize and transgenic maize.[41]