“We apologize for the mistakes,” the authors of the two papers wrote in a retraction.

“These multiple errors impair the credibility of the study as a whole, and we are unable to say without doubt whether the STAP-SC phenomenon is real,” they wrote. “Ongoing studies are investigating this phenomenon afresh, but given the extensive nature of the errors currently found, we consider it appropriate to retract both papers.”

STAP-SC stands for stem cells resulting from stimulus-triggered acquisition of pluripotency. The researchers reported in January that regular cells taken from the body could be turned into stem cells by simply exposing them to stress, as by dipping them in an acid bath.

That seemed to provide an easy way to create multipurpose stem cells that could then be turned into different types of tissues, which might one day be used to treat diseases or repair injuries.

The retraction notices listed five errors that were not previously disclosed in the Riken investigation. Most of them were that images in the papers did not show what they were said to have shown. One error was that cells used in a crucial experiment did not match the mice from which the cells were supposed to have been taken.

While many of the authors of the work at Riken had previously agreed to a retraction, one holdout had been Dr. Charles A. Vacanti of Harvard University and the Brigham and Women’s Hospital, who had been Ms. Obokata’s supervisor when she was a graduate student in his laboratory and was the senior author of one of the papers.