KOBE – The academic scandal over a debunked stem cell discovery has taken a criminal turn, with police questioning the scientist at the center of the storm.

Disgraced researcher Haruko Obokata recently underwent voluntary questioning in connection with the alleged theft of stem cell samples from her former employer, the Riken institute in Kobe, an investigative source said Thursday.

She was questioned in response to a complaint filed by another former Riken researcher in January last year, although Riken itself has not reported any crime, the police said.

The complainant claimed someone had stolen embryonic stem cells from the laboratory in Kobe in or after April 2011, when Obokata was still employed by Riken. She left the institute in disgrace in December 2014.

Riken concluded in February last year that, due to research misconduct over her debunked discovery of “stimulus triggered acquisition of pluripotency” cells, Obokata would have been fired had she not already resigned. She was the lead author of a pair of papers on the subject that were published in the British science journal Nature in January 2014. The research was initially seen as a groundbreaking discovery, but questions about the papers soon emerged, triggering multiple unsuccessful attempts to reproduce her findings.

In April 2014, Riken said Obokata had falsified parts of the reports. Nature retracted the papers the following July.

After failing to duplicate her results, Riken surmised in December that the so-called STAP cells were most likely embryonic stem cells, or ES cells, effectively concluding that STAP did not exist.

A container labeled “ES cells” was found in Obokata’s laboratory during the investigation, but Obokata denied mixing them, intentionally or unintentionally, with the specimens used in her research.

Last month, Obokata published a book recounting the controversy.