Korean biologists recently made headlines with the first successful step toward therapeutic cloning–the creation of master cells genetically identical to a donor from cloned human embryos. Now the researchers, Woo Suk Hwang and Shin Yong Moon of Seoul National University, face serious questions over the methods used to recruit the egg donors that were critical for the study. In February, the team announced that they had not only successfully cloned human embryos, but also produced stem cells–that is, cells capable of becoming any tissue in the body–from those embryos. The work was hailed worldwide, both for its potential to one day provide patients with replacement cells, tissues, or even organs 100% compatible with their own and as the first rigorously reviewed evidence that such cells could be created.

Today, the journal Nature published a story that raises serious questions over the researchers’ recruiting of 16 volunteer egg donors, an astonishingly high number. Among the allegations: one of the study’s junior authors may have been a donor. Korean citizens’ groups and leading bioethicists are pressuring South Korea’s National Human Rights Commission to investigate.

While the researchers may well be exonerated, the fact that such questions have even been raised only fuels the arguments of those who claim that stem cell and therapeutic cloning research are ethical quagmires and that principled, reputable research in these areas is impossible. If the questions aren’t resolved quickly, the consequences for therapeutic cloning research–and in the U.S., even for unrelated embryonic stem cell research–could be disastrous.