Radiation contamination has been found in a leading brand of Japanese baby formula, most likely fallout from the country's crippled nuclear plant, its manufacturer said Tuesday.

Meiji, a major producer of milk, confectionery and pharmaceuticals, said it was recalling some 400,000 cans of "Meiji Step" formula that contained a small amount of radioactive caesium-134 and ceasium-137.

The level of contamination ranged from 22 to 31 becquerels per kilogram (10 to 14 becquerels per pound), compared with the 200-becquerel legal limit, Meiji said.

The formula was produced at a factory in Saitama prefecture, some 200 kilometres (125 miles) from the Fukushima Daiichi nuclear plant, where reactors were sent into meltdown in the aftermath of the March 11 quake and tsunami.

The company said it suspects caesium might have entered the formula during the drying process, rather than being present in the raw materials used, but stressed the exact cause of the contamination was not clear.

The announcement will add to the unease in Japan over food safety, particularly for small children, with a significant proportion of the public mistrustful of official pronouncements on radiation.

The government has previously declared many food items safe to eat, including rice produced in Fukushima after the nuclear disaster, only to announce later that a number of farm products had been contaminated.

Following the latest announcement, shares in Meiji Holdings plunged 9.72 percent to 3,020 yen on the Tokyo Stock Exchange.

The company said no radioactive contamination had been detected in any of its other products.