With two more deaths reported Thursday, a total of four people have died after taking a supplement containing beni k¨­ji (red fermented rice) made by Kobayashi Pharmaceutical, with about 93 hospitalized.

The Osaka-based company and the health ministry are scrambling to find answers as the cause of the death remains unknown. Kobayashi Pharmaceutical, along with other companies who use beni k¨­ji in their products, are issuing voluntary recalls as public concern grows over the substance.

However, experts say that there are no dangers in the beni k¨­ji itself and that the health hazard was most likely caused by some unknown substance that made its way into batches of the supplement produced during a certain time frame.