South Korean authorities have found traces of radioactive substances in food imported from Japan, but said they posed no danger to human health, media reports said Wednesday.

Tests revealed radioactive iodine and caesium in 14 out of 244 products, the Yonhap News Agency reported, citing the Korea Food and Drug Administration (KFDA) in Seoul.

The food items were imported between March 19-29.

Levels of radioactivity in the 14 food items — including melons, bread, biscuits and vitamins — were still well under the maximum allowed levels.

Some of the products were reportedly manufactured before the Fukushima nuclear power plant was damaged by the March 11 magnitude-9 earthquake and tsunami that hit north-eastern Japan.

For that reason it could not be ruled out that in some cases the radioactivity could be traced back to natural sources, the KFDA said.

After the problems at the Japanese reactors low levels of iodine and caesium were discovered in the atmosphere in various parts of South Korea including Seoul.

The Korea Institute for Nuclear Safety in Taejon said on Tuesday that the radioactive iodine-131 probably came from the Fukushima plant.

But the concentration was so low that there was no danger to the environment or human health.