The University of Minnesota has concluded that falsified data were used in a 2001 article published by one of its researchers on adult stem cells. The school is asking that the article be retracted.

The conclusion follows an 18-month investigation into research published by stem-cell expert Dr. Catherine Verfaillie. The investigation clears Verfaillie of misconduct but points to a former graduate student, Dr. Morayma Reyes, who is now an assistant professor at the University of Washington.

The university blames Verfaillie for "inadequate training and oversight," and says it has asked for a retraction of the published article, which appeared in the journal Blood.

Reyes said it was an honest error and there was no intent to deceive.

The study was one of a series that Verfaillie published, suggesting that adult stem cells could be used as an alternative to embryonic stem cells in medical research.

Her research received international attention because of political and ethical controversies over research involving embryonic stem cells. A panel of experts concluded that four images used in the Blood paper were intentionally altered, according to Tim Mulcahy, the university's vice president of research.

Verfaillie, who now lives in Belgium, could not be reached for comment, the Star Tribune reported.

Reyes, who responded to questions by e-mail, said the correction in the journal Blood is warranted. However, she denied falsifying data.

She said the university panel said she falsified data by adjusting brightness and contrast in scientific images included in the article. At the time the research was done, that was an accepted practice but it has since changed, she said. The panel judged her on the newer standard.

Reyes said the errors occurred because of "inexperience, poor training and lack of clear standards" on the handling of digital images. "I regret very much these errors and never had the intention to deceive," she said.

But Reyes also said they in no way altered the conclusions of the paper, and the research has since been successfully reproduced by other scientists.

Mulcahy said it's not clear how, or if, the discovery will affect the underlying findings of the research. "That's an issue that ultimately the scientific community will have to resolve for itself," he said.