Members of the Nuclear Regulation Authority voiced frustration at Tokyo Electric Power (TEPCO), which has failed to identify the source and the cause of spiking readings of radioactive materials in groundwater.
"It is strongly suspected that highly concentrated contaminated waste water has leaked to the ground and has spread to the sea," the authority said in its written review of TEPCO's recent announcements.
The giant utility that services Tokyo and its surrounding regions has said groundwater samples taken at the battered Fukushima Daiichi plant yesterday showed levels of possibly cancer-causing caesium-134 were more than 110 times higher than they were on Friday.
The company has admitted in recent weeks that water and soil samples taken at the Fukushima plant are showing high readings for other potentially dangerous substances, including caesium-137, tritium and strontium-90.
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"I see (TEPCO) has not been able to find the cause of these spikes in readings," NRA Chairman Shunichi Tanaka told a meeting of its commissioners.
"TEPCO says there has not been meaningful impact on the environment. But we must see for sure what are the possibilities of this leading to oceanic contamination," said Toyoshi Fuketa, an NRA commissioner.
The substances were released by the meltdowns of reactors at the plant in the aftermath of the huge tsunami of March 2011, which swamped cooling systems at the plant.