Tokyo, Aug 20 (IANS): At least 300 tonnes of highly radioactive water leaked from one of the storage tanks at Fukushima Daiichi nuclear plant, the worst leakage yet from the tanks, Tokyo Electric Power Co. (TEPCO) said Tuesday.

TEPCO found the leakage Monday as water level in one of the tanks was lowered by about 2.9 metres. The 11-metre-high tank contained about 1,000 tonnes of water before and an estimated 300 tonnes of water is thought to have leaked, Xinhua reported.

The company detected about 80 million becquerels per litre of radioactive substances emitting beta ray, such as strontium-90.

Masayuki Ono, spokesman of TEPCO, told a press conference Tuesday that the leakage is continuing and leaked water has most likely seeped into the ground but not into the sea.

TEPCO is now trying to prevent the spread of radioactive water and remove the contaminated soil, said Ono.

The plant has struggled with a series of radioactive water leaks and power failures since March 2011 when an earthquake-triggered tsunami destroyed its power and cooling systems, causing multiple meltdowns.

The storage tanks were built around the plant to store radioactive water leaked from the reactors.