New scientific studies on the impact of genetically engineered corn on monarch butterflies say the corn is having virtually no effect. The story says that the papers also make the provocative claim that earlier studies raising the question might have been flawed.

But the debate is far from ended.

The story says that the earlier papers reported that many monarch caterpillars died after ingesting pollen from the genetically modified corn.

The new papers say that the pollen used in those experiments appeared to be mixed with other parts of the genetically modified plants and that it was those plant parts, not the pollen, that actually killed the caterpillars.

John Obrycki, a professor of entomology at Iowa State University and an author of one of the earlier reports, was quoted as saying, "It's part of what's naturally deposited in the field."

While critics of genetically modified food have not yet seen the papers which were released on Friday night to the press but not yet to the public they are already pointing to this pollen issue. They also note that the studies addressed the short-term impact of the crop, which is called BT corn, but not the longer- term impacts of low levels of exposure to the pollen.

Rebecca Goldburg, senior scientist at Environmental Defense, an environmental group, was quoted as saying, "The results suggest that the major BT corn varieties on the market are not immediately lethal to monarch butterfly caterpillars. They don't take a very hard look at what might be called sublethal effects long term."

Even some of the authors of the new papers were hesitant to say that the question is completely settled, though concerns are certainly less than they were before.

May R. Berenbaum, a professor of entomology at the University of Illinois who edited the six new papers, which will be published online this week by The Proceedings of the National Academy of Sciences, was quoted as saying,"I don't think there's a near and present danger."