Tokyo Electric Power Co. said it found radioactive substances in a drainage ditch that leads directly to the Pacific Ocean near the Fukushima No. 1 nuclear plant.
Substances radiating 220 becquerels per liter were found in samples taken Wednesday from a ditch about 150 meters from the sea. The beta rays given off by strontium, cesium and other substances were some 12 times greater than samples taken there Tuesday, Tepco said Thursday.
Workers have been trying to decontaminate an upstream ditch for several days, and Tepco suspects toxic water seeped through sandbags placed there.
The upstream ditch is near a water tank in the area known as H4 from which around 300 tons of highly toxic water was recently found to have leaked.
The latest finding could undermine Prime Minister Shinzo Abe's remarks during Tokyo's final presentation to the International Olympic Committee in Buenos Aires last weekend that the radioactive leakage has been "completely confined," before Tokyo won the 2020 Olympics.
Tepco said it has not taken measures to prevent the radioactive substances in the ditch from reaching the sea.
The utility maintains that no abnormalities have been detected in the radiation levels of the seawater, with its evaluation based on samples taken about 100 meters south of the drainage outlet.
The level of bone-cancer-linked strontium-90, which makes up about half of the beta ray-emitting substances detected in samples from the ditch, is believed beyond the threshold set by the government.
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