The science ministry said Saturday a minuscule amount of radioactive substances was detected in tap water in Tokyo, as well as Tochigi, Gunma, Chiba and Saitama prefectures.
It is believed the water carried traces of radioactive iodine. Meanwhile, traces of radioactive cesium were also found in tap water in Tochigi and Gunma.
In addition, milk and spinach from areas near the crippled Fukushima No. 1 nuclear plant have also been found with radiation above the regulated standards, Chief Cabinet Secretary Yukio Edano said the same day.
Edano, however, said the levels of radiation detected do not immediately pose a risk to human health and asked consumers to remain calm.
"It's not as if you would be harmed if you ate it right away," he said. "It would be harmful to continue to eat it for some time."
The milk from the town of Kawamata, Fukushima Prefecture, was collected between Wednesday and Friday, and the contaminated spinach, from six municipalities in Ibaraki Prefecture, was picked Friday, according to the health ministry.
Edano said the government will investigate.
Vice Health Minister Kohei Otsuka said that if confirmed, sales of the contaminated products will be stopped and they will be recalled.
Dairy farmers in Fukushima Prefecture, whose businesses were already rocked by the March 11 quake and tsunami, were shocked by the finding.
A 63-year-old woman who takes care of about 80 milk cows in the town of Kawamata said she wondered what would happen to her farm, which has already been forced to suspend operations due to a lack of fuel for transporting the milk.
Other people involved in dairy farming in Fukushima said they fear baseless rumors will spread that all dairy products from the region are contaminated with deadly substances.
