Shares in Tokyo Electric Power Co. Plunged 17.73 per cent on Monday amid criticism over its handling of a deepening crisis at its stricken Fukushima Daiichi nuclear plant.
Tepco closed at 696 yen — less than a third of their close of 2,121 yen on March 11, minutes after Japan was hit by its biggest ever recorded earthquake and a tsunami but before the disaster triggered a nuclear crisis.
Radiation from the plant Northeast of Tokyo has wafted into the air, contaminating farm produce and drinking water, and seeped into the Pacific Ocean, although officials stress there is no imminent health threat.
Engineers are racing to restore cooling systems knocked out by the tsunami.
The company came under fire on Monday, a day after it erroneously said radiation in water at the stricken site had reached 10 million times the normal level, later issuing a much lower — but still dangerous — figure.
"Considering the fact that the monitoring of radioactivity is a major condition to ensure safety, this kind of mistake is absolutely unacceptable," said top government spokesman Yukio Edano.