A Japanese drugmaker said Monday that 26 people had been hospitalised in relation to health supplements the company has recalled because of concerns over kidney problems.

The prescription-free supplements contain a type of yeast-fermented rice called "beni koji", which Kobayashi Pharmaceutical reportedly says it has supplied to around 50 other firms worldwide.

The drugmaker on Friday said it was voluntarily recalling three products containing beni koji, which aims to lower bad cholesterol, after customer complaints.

On Monday the Osaka-based firm said it was aware of 26 hospitalisations, but had "not yet reached a conclusion" on a potential link between the product and kidney issues.

"After analysis... we found a possibility that the raw materials used to make beni koji may contain ingredients that our company had not intended to include," Kobayashi Pharmaceutical said.