Radioactive caesium believed to have come from the Fukushima nuclear plant has been found in a brand of Japanese baby formula.
Caesium levels of up to 31 becquerels per kilogram have been found in baby formula made by the Meiji Corporation.
While it is below the government-set allowable limit of 200 becquerels per kilogram, there are concerns that babies are more susceptible to the harmful effects of radiation.
The company suspects a link between the contamination and the meltdowns at the Fukushima nuclear plant, saying hot air used in the drying process may have contained caesium.
It is now recalling 400,000 cans of the formula which are believed to have been contaminated.
Shares of Meiji Holdings plunged nearly 10 per cent to their lowest close since May 2009 following the news.
Worries over the safety of food supplies have shaken the public after the March 11 earthquake and tsunami crippled the Fukushima plant in the worst nuclear accident in 25 years, spreading radiation over a large swathe of northern and eastern Japan.
Cases of excessive radiation in vegetables, tea, milk, seafood and water have stoked anxiety despite assurance from public officials that the levels detected are not dangerous.
TEPCO, the operator of the Fukushima plant, this week said about 45 tonnes of contaminated water had leaked from a system that cleans radiated water, of which the utility said 300 litres escaped outside.
