A Japanese drugmaker whose dietary supplements are at the centre 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 hospitalised.

"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 composition.

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

Government spokesman Yoshimasa Hayashi said on 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. (AFP)