A highly carcinogenic toxin was detected in Thai rice imported by Japan in June and sold to a domestic processed food maker, the farm ministry said Friday.
The revelation marks the first time aflatoxin, a poisonous substance produced by fungi, has been found in rice imported for edible use.
The processed food maker has already manufactured products with the tainted rice, after removing around 180 grams of the toxic fungi, but has not made any shipments, the Agriculture, Forestry and Fisheries Ministry said.
In a bid to secure food safety, the ministry said it has ordered the firm not to ship any of the products.
The rice in question was part of 3,508 tons that arrived from Thailand in late June in line with Japan's obligation to import a certain amount of rice each year under a World Trade Organization "minimum access" deal.
The incident came to light after the food maker found fungi in one of the 24 1-ton containers it purchased in late October and notified a local agricultural office.
The ministry said a panel of scientific and technical experts will investigate.
The ministry will not reveal the name of the food maker as it has not shipped any food products made with the rice.
No toxins have been detected in the Thai rice sold to other firms or in the unsold inventory of about 3,421 tons.