Genetically modified corn poses a "negligible" risk to monarch butterflies, according to a package of six papers that will soon be published in a scientific journal.

The papers, the most comprehensive peer-reviewed publications on this issue, could lay to rest one of the biggest controversies over genetically modified crops.

"I don't think there's a need to consider monarchs at risk due to this technology," said Mark K. Sears, a professor of environmental biology at the University of Guelth in Ontario, a lead author on one of the papers. Drafts of the papers were released late yesterday by the Proceedings of the National Academy of Sciences and will be published next week, ahead of an Oct. 1 release that had been planned.

The early release came because the Environmental Protection Agency is scrambling to defuse criticism that it has been planning to renew the permits for these genetically modified crops even though the data on the butterfly impact had not yet been widely released to the public.

The E.P.A. has been planning to announce its decision on the crops - corn and cotton engineered to kill pests that feed on them - by Sept. 30, when the old permits expire. But that would have been a day before the monarch butterfly studies were to be published.

Critics of genetically engineered foods said the timetable represented an attempt to stifle debate on the crops. So on Thursday, the E.P.A. asked the journal to publish the papers earlier.

The E.P.A. is also considering postponing its decision date on the crops, said a spokesman, David Deegan. But he said the agency could not wait too long because farmers needed to know by fall what seeds would be available for next year's planting.

The crops in question, known as BT corn and cotton, contain a bacterial gene that causes the plants to produce a toxin that kills pests. The crops with the BT toxin are one of the two major products of the plant biotechnology industry, the other being crops with a gene for herbicide resistance. About 19 percent of the corn and 35 percent of the cotton planted in the United States in 2000 had the BT gene, according to the Department of Agriculture. But controversy has swirled around the crops since 1999, when Cornell University scientists reported that some monarch butterfly caterpillars had been killed when they ate pollen from BT corn in a laboratory experiment. The new studies, financed by the agricultural biotechnology industry and the government but carried out mainly by academic scientists, address whether the effects seen in the laboratory are also found in the field.

The papers say there is little risk to monarchs from the two main types of BT corn grown because the pollen is not toxic in the concentrations that monarch larvae would encounter in the fields.

The studies did find that one type of BT corn, known as Event 176, would harm some butterflies because it has extremely high levels of the bacterial toxin in its pollen. But that type of BT corn is rarely planted and is being withdrawn from the market.

Jane Rissler of the Union of Concerned Scientists, an advocacy group critical of genetically engineered crops, said the studies showed the E.P.A. had not adequately assessed the risks before approving Event 176. The monarchs "lucked out," she said because Event 176 proved unpopular with farmers.

Still, the studies could help lay to rest much of the controversy. The E.P.A. is widely expected to renew the permits for the crops. The question, however, is what kind of requirements growers will have to adhere to, like how much of their fields must be reserved for nonmodified crops to prevent insects from becoming resistant to the BT toxin.

Until now, the study results, while they have been supplied to the E.P.A. by the industry, have been classified as "confidential business information" by the agency. The information has been kept from widespread public view so as not to jeopardize the chances that the papers would be published. Many scientific journals will not accept papers that have been too widely disseminated beforehand.

One scientist involved in the butterfly research, Dr. Karen S. Oberhauser of the University of Minnesota, called for the E.P.A. to delay its decision until opponents of genetically modified crops had a chance to review the data.

"The procedure has stifled thoughtful scientific debate on this issue," Dr. Oberhauser, an ecology professor, wrote to the E.P.A. last Saturday. She said that while she agreed with the overall conclusion that the main types of BT corn did not pose a risk to the monarchs, she said that the industry's summary of the data, which the E.P.A. had been relying on, contained several misleading statements in support of that conclusion. Some of the other scientists involved in the research disagreed with Professor Oberhauser. Dr. Galen P. Dively, a professor of entomology at the University of Maryland, said the scientists had all signed statements saying that the industry summaries submitted to E.P.A. accurately represented the scientific findings. "I don't understand why the critics are so concerned about it," he said.

Dr. Rissler of the Union of Concerned Scientists said the agency "betrayed its promise" to have a transparent decision-making process. "The monarch issue was probably the biggest environmental issue associated with any genetically modified crop thus far, and it seemed appropriate that the public should see the data before the decision is made," she said. Biotechnology industry officials said that only 27 pages of information had been kept confidential out of the hundreds submitted. Moreover, starting about two weeks ago, even those 27 pages could be viewed by the public in 11 E.P.A. reading rooms around the country. But those who view the data must sign an agreement not to copy it or discuss it with others, although they can submit confidential comments to the E.P.A.

The E.P.A. routinely requires that some information not be disclosed to a company's competitors. But this extra nondisclosure agreement, drawn up by the agricultural biotechnology industry, appears to be unusual, and some environmentalists said it was too restrictive.

Stanley H. Abramson, a lawyer in Washington who represents agricultural biotechnology companies, said the industry saw the study results as favorable and would have been happy to have them released earlier but did not want to jeopardize the academic scientists' chances of publication. But Dr. Nicholas R. Cozzarelli, the editor in chief of The Proceedings of the National Academy, said he was not aware of the nondisclosure agreement. Dr. Cozzarelli, a professor at the University of California at Berkeley, said that if the data had been open for public viewing, "it would not have compromised publication in the slightest."

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