Puberulic acid produced by blue mold is the cause of kidney problems suffered by consumers of Kobayashi Pharmaceutical¡¯s beni k¨­Âá¾± (red yeast rice) supplements, the health ministry said Wednesday.

The finding came at the end of the ministry¡¯s monthslong probe into the supplements, which sparked a health crisis in Japan and abroad among people who took them.

While the ministry had been aware of puberulic acid as a possible cause of the kidney problems, the detection of two unknown chemical compounds kept it from making that finding conclusive.

But those two compounds, identified as Y and Z and collected from Kobayashi Pharmaceutical¡¯s factories in Wakayama and Osaka prefectures, were found to have caused no harm to the kidney in a seven-day trial using rats, the ministry said.

The puberulic acid is believed to have been produced by blue mold, which was found during the inspection of Kobayashi Pharmaceutical¡¯s factories by the health ministry. The puberulic acid likely fed off a rice culture medium used in the manufacturing process of beni k¨­Âá¾± pills, the ministry officials said.

As of Sunday, 116 people have died while 502 others have been hospitalized after taking the pills, according to data reported to the ministry by the firm.

Now that the toxic substance has been identified, the ministry will consider measures to toughen up manufacturing standards and hygiene management protocols for dietary supplements to prevent recurrences, officials said.

The issue has forced a major restructuring of the Osaka-based drugmaker, including the resignations of the firm¡¯s chairman and president.

This month, the government introduced a system to make it mandatory for businesses to report health damage that arises from the consumption of dietary supplements and other food products labeled as health-enhancing foods.

The measure is aimed at allowing government agencies to quickly collect health-related information and prevent the spread of incidents similar to what happened at Kobayashi Pharmaceutical. According to the Consumer Affairs Agency, businesses were previously asked to report health damage under related guidelines, but they lacked teeth as they had no specified deadlines.

Meanwhile, a man in his 40s has recently filed a civil suit against Kobayashi Pharmaceutical, saying he developed kidney problems after consuming the firm¡¯s pills, Jiji Press reported.

According to the lawsuit filed at the Osaka District Court on July 12, the man was diagnosed with drug-induced acute kidney injury and acute tubular damage by a hospital. He is demanding ?5 million ($35,250) in damages from Kobayashi Pharmaceutical, saying the firm failed to promptly announce reports of the health damage associated with its pills.