Japanese drugmaker Kobayashi Pharmaceutical says it last year shipped "beni-koji" red yeast rice materials including powdery substances that were mistakenly dropped on the floor at its Osaka plant.
A number of people developed kidney diseases and other illnesses after taking the firm's supplements that contain "beni-koji" ingredients.
But the company said the shipped materials were not used to produce the supplements and they managed to recover most of the batch. It says the materials were intended for coloring food or other purposes.
The firm said that in April last year, workers at the plant forgot to close a lid of a machine for blending substances used to produce "beni-koji" materials. As a result, 33 kilograms of powdery substances accidently fell on the floor.
The company said workers scooped up some of the powder that did not come in contact with the floor. After making sure that there was no problem with the quality, workers mixed the powder with other substances and shipped the product as "beni-koji" materials.
Osaka Mayor Yokoyama Hideyuki indicated that the city will investigate whether there was any problem with the plant's sanitary management.
He said he does not think the incident is directly linked to the problems related to the supplements. But he added that it is questionable whether the workers' actions were right in terms of sanitary awareness.
Kobayashi Pharmaceutical said the acts were inappropriate in light of its sanitary management policy. The firm added that it will make utmost efforts to avoid causing troubles and raising concerns.