The government on Thursday banned rice shipments from another area in Fukushima Prefecture, after local authorities found high levels of radioactive cesium.

Samples of the rice, which was harvested by just one farmer in the Shibukawa area of the city of Nihonmatsu, were found to contain 780 becquerels per kilogram of cesium, said Shin Sato at the farm ministry. The maximum level is 500 becquerels per kilogram.

The farmer in Shibukawa harvested 1 ton of rice this year, and hasn't sold any of his crop. All the rice is being kept in storage by the farmer and his neighbors.

The discovery came as authorities increased their inspections of rice, after tainted samples were found in areas of the cities of Fukushima and Date.

In October, Fukushima Gov. Yuhei Sato declared that rice produced in the prefecture was safe for consumption.

But the discovery of contaminated rice in Shibukawa means that as of Thursday, rice with excessively high levels of cesium has been found in five areas in three cities — all in Fukushima Prefecture.

"We may find more contaminated rice in other areas," Shinji Uchida from the farm ministry said Thursday. "The limited capacity for testing means local authorities were unable to check every bag of rice for contamination."

The government allowed farmers in Fukushima Prefecture to start shipping rice in October, after test results failed to detect excessive levels of cesium.

Contaminated rice in the prefecture was first detected in November, when a farmer in the city of Fukushima voluntarily submitted samples from his harvest for testing at a local agricultural group.