SENDAI, Japan —
Tap water in several areas of Japan, including Tokyo, has shown higher-than-normal levels of radiation. In the capital, readings were at one point two times higher than the government safety limit for infants, who are particularly vulnerable to radioactive iodine.
But levels have fallen steadily since peaking Wednesday, and Tokyo metropolitan officials said Saturday that tap water was now safe for babies to drink.
Just outside a reactor at the coastal nuclear plant, radioactivity in seawater tested some 1,250 times higher than normal, Nishiyama said. He said the area is not a source of seafood and the contamination posed no immediate threat to human health.
However, tests conducted 18 miles (28 kilometers) offshore found radioactive iodine-131 at levels nearing the regulatory limit set by the Japanese government, the International Atomic Energy Agency said. The tests also detected another radioactive substance, cesium-137, at lower levels.
IAEA experts said the ocean will quickly dilute the worst contamination. Radioactive iodine breaks down within weeks but cesium could foul the marine environment for decades.
Nuclear safety officials suspect a breach in one or more of the plant's units, possibly a crack or hole in the stainless steel chamber around a reactor core containing fuel rods or the concrete wall surrounding a pool where spent fuel rods are stored.
Suspicions were aroused when two workers suffered skin burns after unexpectedly encountering water that was 10,000 times more radioactive than levels normally found in the units, NISA said.
Such a breach could mean a much larger release of radioactive contaminants than had been thought. The most likely consequence would be contamination of the groundwater, experts said.
Radioactivity was on the rise in some units, Nishiyama said Saturday.
"It is crucial to figure out how to remove contaminated water while allowing work to continue," he said, acknowledging that the discovery would set back delicate efforts to get the plant's cooling system operating again.