Kobayashi Pharmaceutical Co. said Friday that it has confirmed a fifth death possibly linked to its red yeast rice dietary supplements, but has yet to determine the substance that may be responsible for causing health problems amid hundreds of reports of people falling ill.

The drugmaker as well as Japan's health ministry said the company's examination unexpectedly found puberulic acid, a natural compound made from blue mold, in the products. The ministry said the substance is a potent antibacterial and antimalarial agent that can be toxic.

An official of the Health, Labor and Welfare Ministry said there is "a certain degree of possibility" that puberulic acid may have caused the health problems, but the ministry will conduct thorough examinations.

Kobayashi Pharmaceutical Co. President Akihiro Kobayashi (C) attends a press conference in the western Japan city of Osaka on March 29, 2024.  (Kyodo)

The five deaths include people who were in their 70s to 90s, according to the company, which has recalled the supplements that were supposed to help lower levels of LDL cholesterol, known as "bad" cholesterol.

Some 680 people have received or wish to receive outpatient treatment for symptoms suspected to be linked to the "beni-koji choleste help" supplements so far, and the company will offer them compensation along with the 114 people who have been hospitalized, it said.

"Determining a cause and preventing (the incident) from occurring again is our responsibility. I will make sure as the company's head to get that done," Kobayashi Pharmaceutical President Akihiro Kobayashi said in a press conference.

Supplied photo shows Kobayashi Pharmaceutical Co.'s dietary supplements that contain "beni-koji," which are being recalled over health problems. (Kyodo)

Kobayashi said the substance in question "could have been derived from mold, but we have yet to ascertain which (chemical) structure it has."

A government research facility is set to conduct a further examination of the substance in collaboration with the company, the ministry said.

At the press conference held in Osaka, there were many questions about the slow response to the health problems by management. The company said it first noticed there was a potential problem in January, but it did not go public about the matter until March 22.

Kobayashi said it took the company time to speak publicly about the problems because it struggled to identify the cause of the issues.

The fallout from the scandal has spread overseas. Taiwanese media reported Thursday that a woman who consumed supplements containing the company's red yeast rice was diagnosed with acute kidney failure.

The drugmaker announced on March 22 that people who took the supplements were experiencing symptoms such as kidney disease.

The company initially suspected the involvement of citrinin, a toxic metabolite produced by red yeast rice, but later said the substance had not been detected in its products.

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