The International Academy of Cytology says the death of two patients in South Korea who received stem cell transplants cannot be blamed on the stem cell operation.

Citing probe results, the academy says the operations cannot have directly caused the death of the patients, as one patient died two weeks after the transplant and the other patient died of pulmonary embolism.

The academy added that there aren’t any plausible ethical disputes as the patients were sufficiently briefed by doctors beforehand and were made aware of the possible side effects of the operation.

The International Academy of Cytology is an organization of 500 doctors and experts from 35 countries dealing with the study of cells.