A Japanese drugmaker whose dietary supplements are at the center of a growing health scare reported on Thursday two more deaths potentially related to its tablets.

Last week, Kobayashi Pharmaceutical recalled three supplement brands — "Beni Koji Choleste Help" and two others — after customer complaints of kidney problems. 

The over-the-counter products contain an ingredient called red yeast rice, or "beni koji", which is supposed to help lower cholesterol.

Thursday's announcement brings the total number of deaths under investigation by the company and health ministry to four, with more than 100 other people hospitalized.

"We were told yesterday by a bereaved family that a person who had been using Choleste Help had passed away due to kidney disease," the drugmaker said in a statement.

It added it had been told separately that another person who had used Choleste Help in recent years had died.

"We are in the process of confirming the facts and causal relationships in both of these cases," the statement said.

"However, we decided to make this report public from the viewpoint of prompt disclosure."

Medical studies describe red yeast rice as an alternative to statins for lowering high cholesterol, but also warn of a risk of organ damage depending on its chemical make-up.

Kobayashi Pharmaceutical sells a wide range of health products marketed through television adverts in Japan.

The Osaka-based company says it has also supplied red yeast rice to around 50 other firms in Japan and two in Taiwan.

Government spokesman Yoshimasa Hayashi said Thursday that authorities were doing "their utmost to ensure food safety, including identifying the substance that caused the health harm and how it became present in the product".

The government has ordered various health-food makers to review their products, while informing foreign countries about the issue through Japan's embassies, he said.

Dozens of Japanese firms that used beni koji provided by Kobayashi Pharmaceutical have also separately announced recalls.

The affected products include health tablets as well as a rose-coloured sparkling sake, salad dressing, bread and miso paste used in many traditional dishes.

Kobayashi Pharmaceutical has said analysis had found a possibility that the products contained "ingredients we had not intended to include".

But it said it did not find any citrinin produced by red yeast rice, which is toxic and can damage the kidneys.