TOKYO: More than 350 people have been sickened across Japan after eating frozen food products that may have been tainted with a pesticide, Japanese public broadcaster NHK reported Tuesday.

Food maker Maruha Nichiro Holdings began recalling 6.4 million packages of various frozen foods on Dec 29, saying it found some were tainted by high levels of pesticides.

The company has received hundreds of thousands of calls about the problem.

NHK said information from local governments showed 356 people suffered vomiting, diarrhea and other problems after eating items subject to the recall, which include a wide range of products such as frozen pizzas, croquettes and lasagna.

It was unclear, however, if consumption of the tainted products was directly responsible for the illnesses, NHK said.

Maruha Nichiro says it has retrieved about 1.1 million packages subject to the recall so far. Last week, it issued a formal apology and appealed to consumers not to eat any of the affected products.

Police are investigating how the items were contaminated with the pesticide malathion, reportedly by up to 2.6 million times the allowable limit. The tainted products were produced by a factory in northern Japan's Gunma prefecture.

Malathion is a pesticide used in farming and gardening and also to kill fleas on animals and people. At high enough concentrations, it can cause death, according to the US Centers for Disease Control.

There have been no reports of life-threatening illnesses from Maruha's products, but the contamination has further shaken public confidence undermined by various food quality scandals.

Late last year, a slew of top-notch hotels and department stores apologised after it was found that some of the items they were selling were actually cheaper substitutes.

Local magazines are also warning that trade agreements with other countries like China might lead to imports of contaminated or otherwise unsafe products.