At the intersection of cocaine and Roundup in rural South America, Monsanto and the U.S. government are struggling to keep up appearances. That’s becoming more and more difficult as the unanticipated hazards of genetic modification become clearer.

Back in April, Argentinean embryologist Andrés Carrasco gave an interview with a Buenos Aires newspaper describing his recent findings suggesting the chemical glyphosate, a chemical herbicide widely used in agriculture as well as in U.S. anti-narcotic efforts, could cause defects in fetuses in much smaller doses than those to which peasants and farmers in his country were already being exposed. Loud calls for a ban on the substance were issued by Argentinean environmental lawyers, and the country’s Ministry of Defense banned the planting of glyphosate-resistant soya crops in its fields.

Then came the backlash. An article in an Argentinean paper recently reported that Carrasco was assaulted in a way he described as “violent” by four men associated with agricultural interests:

Two of the men were said to be members of an agrochemical industry body but refused to give their names. The other two claimed to be a lawyer and notary. They apparently interrogated Dr. Carrasco and demanded to see details of the experiments. They left a card Basílico, Andrada & Santurio, attorneys on behalf of Felipe Alejandro Noël.

It’s still unclear who these people are. But the interest in keeping such information quiet or discrediting Carrasco and his findings are strongest with Monsanto, the agricultural company who first patented a glyphosate product (sold as Roundup) and also created genetically-modified crops specifically to resist the herbicide.

GRAIN, an international non-profit supporting small-scale farmers and biodiversity in community agriculture, originally reported the story, evidently before the reports of threats against Carrasco were known. GRAIN has also done extensive reporting on Monsanto’s genetically-modified soya crops in Argentina (which, according to the group, have increased five-fold since their introduction there, and have taken over more than half of Argentina’s farmland) as well as on the use of glyphosate (which has increased fourteen-fold since its introduction, contrary to Monsanto’s promises that its crop would decrease pesticide use). The so-called “Roundup Ready” crops have interbred with other plants, creating “superweeds” which in turn necessitate the use of other poisonous herbicides such as atrazine.

The dangers of glyphosate are hotly debated. The U.S. Environmental Protection Agency does regulate the allowable amount in drinking water, but the data it has on the dangers of the chemical are all nearly two decades old, and many studies were sponsored by Monsanto. But rural agricultural workers across South America have been protesting the spraying for well over a decade, pointing to increases in local cancer rates and birth defects as proof.