A senior Japanese scientist embroiled in a stem-cell research scandal has apparently committed suicide, according to police.

Yoshiki Sasai had supervised and coauthored stem cell research papers that had to be retracted due to falsified contents.

Hyogo prefecture police said on Tuesday that Sasai, 52, was found at a government-affiliated science institute RIKEN in Kobe, western Japan.

Sasai was deputy chief of RIKEN's Centre for Developmental Biology.

A security guard found him suffering from cardiac arrest with a rope around his neck, according to RIKEN.

Sasai was rushed to a hospital but was pronounced dead two hours later.

Police said Sasai left what appeared to be suicide notes but refused to disclose their contents.

Public broadcaster NHK said he had three letters addressed to a coauthor of the research papers, as well as senior members of the research centre and his fellow researchers.

Alleged malpractice

Sasai's team retracted the research papers from British science journal Nature over the alleged malpractice by a fellow researcher, which is being contested.

Retractions of papers in major scientific journals are extremely rare, and the scandal was a major embarrassment to Japanese scientific research.

In two papers published earlier this year in Nature, the researchers reported that they successfully transformed ordinary mouse cells into versatile stem cells by exposing them to a mildly acidic environment.

Scientists hope to harness stem cells to grow replacement tissue for treating a variety of diseases.

RIKEN later held another author of the research responsible for falsifying data.

An investigation by RIKEN found that Sasai and two other employees were not guilty of research misconduct.

Sasai had said he was "deeply ashamed" over the problems in the papers.

Source: Associated Press