South Korea has detected minuscule traces of radioactive particles in agricultural products after conducting radiation checks on 40 locally produced agricultural products, the Ministry for Food, Agriculture, Forestry and Fisheries said on Tuesday.

The ministry said that traces of radioactive iodine and cesium were found in 3 food items including lettuce grown on the southernmost resort island of Jeju and spinaches grown in Tongyeong and Namhae on the southeastern coast.

South Korea had conducted radiation checks on samples of some 40 farm products starting Friday amid growing concerns that Thursday's rain in the country could have brought radiation from Japan's crippled nuclear plant.

The legally permitted levels for iodine and cesium in vegetables are 300 becquerels per kg and 370 bq/kg, respectively.

"Amounts found in the three samples were so small that people should not be worried about ill effects," the ministry claimed.

The ministry also said no radiation has been found in 10 samples of raw milk produced by domestic cows on Jeju Island as well as in 23 samples from domestically caught fishery products.

The ministry, however, said that it will step up radiation monitoring in order to alleviate public worries.