Shares of Tokyo Electric Power Co. plunged Tuesday to their lowest point ever amid growing doubts about its ability to contain the nuclear crisis at the Fukushima No. 1 nuclear power plant.

Tepco shares dropped by ¥80 — the maximum daily limit, or 18 percent, to just ¥362 — falling below its previous all-time closing low of ¥393 from December 1951.

The Fukushima No. 1 plant has been leaking radiation since the March 11 quake and tsunami knocked out its reactor cooling systems, leading to explosions and fires. The plant most recently has leaked radioactive water into the sea.

Tepco's shares have nose-dived 80 percent since March 11. The Tokyo Stock Exchange said investors dumped ¥1.06 trillion worth.

"Investors are continuing to sell Tepco shares due to uncertainty over the nuclear crisis. Especially, yesterday's move to dump radioactive water into the ocean unnerved investors," said Kazuhiro Takahashi, equity analyst at Daiwa SMBC Securities Co. Ltd.

Tepco said Monday it would release low-level radioactive water from the crippled nuclear complex to make room for the storage of more highly radioactive water that has been hampering efforts to stabilize the reactors.

The utility is facing massive compensation claims that analysts estimate will be in the trillions of yen.

The company said Tuesday it would postpone the release of its annual earnings report, scheduled for April 28, due to the crisis. It declined to give further details.

Tepco Vice President Takashi Fujimoto declined to speculate on the board's future.

"Questions are being raised about managerial responsibility, but I don't know what will happen to the board membership," Fujimoto said.