Transgenes from genetically modified (GM) maize crops have been found in traditional maize in Mexico.
The discovery could reignite the GM debate in the country. GM maize was banned in 1998 to protect around 60 domesticated landrace maize varieties and wild relatives but farmers are said to have planted at least 70 hectares of GM maize in the north of the country.
Scientists conducted genetic tests on thousands of maize seed and leaf samples. They found transgenes in about one per cent of more than 100 sampled fields.
Elena Alvarez-Buylla of the National Autonomous University of Mexico, co-author of the study, called for the urgent creation of "rigorous molecular and sampling criteria for biomonitoring at centres of crop origination and diversification".
Her study is one of a series by different authors that have found evidence for and against transgene contamination in Mexico since 2001.