A Japanese government-funded laboratory said Tuesday it is considering retracting a research paper describing a simple way of turning ordinary cells from mice into stem cells.

The Riken Center for Development Biology in Kobe, Japan, has been looking into questions raised over images and wording in the paper, co-authored by lab scientist Haruko Obokata.

Riken said Tuesday that it may retract the paper because of credibility and ethics issues, even though an investigation is continuing.

The paper was published in the scientific journal Nature in late January. It was praised as a possible groundbreaking method for growing tissue for treating illnesses such as diabetes and Parkinson’s disease using a simple lab treatment.

Riken and Nature are investigating allegations including anomalous lines in an image of DNA fragments and a partial plagiarism.

Another author, University of Yamanashi professor Teruhiko Wakayama, said Monday that he believed his part of the research—stem cell production by using the cells provided by Obokata—was appropriate but wanted a third party to run detailed analysis on the stem cells produced. He said he’d rather drop the paper and resubmit it after addressing all questions.

The two scientists were part of a group of researchers, in Boston and Japan, who exposed cells from spleens of newborn mice to a more acidic environment that they’re used to. That turned them into stem cells, they said. Cells from other tissue of newborn mice appeared to go through the same change, which could be triggered by exposing cells to any of a variety of stressful situations.

Scientists hope to harness stem cells to replace defective tissue in a wide variety of diseases. By making stem cells from the patient, they can get around the problem of transplant rejection.