Investigators at Japan’s Riken institute have discredited scientist Haruko Obokata's research papers on so-called stap cells.

Originally published in January, the papers alleged a major discovery - a simple way to turn any cell into a stem cell.

Stem cells can grow into any type of cell and be used in regenerative medicine.

But doubts about the papers surfaced last month, and an investigation was launched.

A special committee of Riken scientists now says photographic evidence was pulled from Obokata’s doctoral thesis and fraudulently altered.

The committee also alleges that Obokata copied charts from another researcher's work.

Riken is dissatisfied with Obokata’s research notebooks, saying they don't present sufficient documentation for three years' worth of scientific research.

Obokata will be held solely responsible for the falsified paper.

Riken has yet to announce the penalties Obokata will face.

Obokata maintains the discovery of stap cells is genuine.

She is expected to refute the allegations in a formal letter to Riken.