French scientists released a study this week that claims rats who were fed Monsanto’s genetically modified corn developed tumors and had multiple organ damage. However, the report is being viewed skeptically by the world community after GM crops have been in the food supply in the United States for more than a decade without showing the same incidence of tumors or organ damage.

Gilles-Eric Seralini of the University of Caen and colleagues said rats fed on a diet containing NK603—a seed variety made tolerant to Monsanto's Roundup herbicide—or given water with Roundup at levels permitted in the United States, died earlier than those on a standard diet, Reuters reported.

Experts not involved in the study were highly skeptical about its methods and findings, with some accusing the French scientists of going on a "statistical fishing trip."

The criticism stems from the scientists’ omission of data on how much the rats were given to eat and that they had used rats that were known to be susceptible to tumors.

“This strain of rat is very prone to mammary tumors particularly when food intake is not restricted. The statistical methods are unconventional … and it would appear the authors have gone on a statistical fishing trip,” said Tom Sanders, head of the nutritional sciences research division at King’s College London.

Monsanto responded to the study by saying it would review the study thoroughly.

“Numerous peer-reviewed scientific studies performed on biotech crops to date, including more thana hundred feeding studies, have continuously confirmed their safety, as reflected in the respective safety assessments by regulatory authorities around the world,” Monsanto spokesperson Thomas Helscher told Reuters.

The release of the results comes within days of France announcing it would continue its temporary ban on Monsanto’s MON810 corn. The government said it was still testing to determine the safety and environmental impact GM crops had. Some speculate that the timing of the study is aimed at keeping GM crops out of Europe. Last week, the European Court of Justice determined that genetically modified crops cannot be subject to individual nation’s authorization because the European bloc already approved their use and marketing. However, with the release of the new data, the authors are calling for renewed testing of all GM crops in two-year  lifelong studies.

Meanwhile, in the United States, the new study will undoubtedly add fuel to the fire in the debate over Proposition 37 in California, which seeks to require food companies to label ingredients that come from genetically modified foods. Monsanto and several other agribusinesses have been funding a campaign to oppose the passage of Prop 37.