Japan's infamous nuclear power plant Fukushima leaked tons of radioactive water into the ground on Tuesday, while its operator is still unsure, what could have cause the leak.

The Nuclear Industrial Safety Agency reported on Tuesday the leakage of about 15 tons of radioactive water from storage tanks of the broken power plant north of Tokyo.

The breach could be repaired until Tuesday afternoon, but to date the cause of the leak is undiscovered, while the plant's operator Tokyo Electric Power Co works on identifying it.

Radiation levels in the leaked water are said to be low, while the it cannot be said with certainty, what will be the effect on the subterranean water of the surrounding area. The storage itself is filled with vast amounts of water at varying contamination levels, which were used in the reactor's cooling system, before the plant was hit by earthquake and tsunami on March 11.

Operator Tepco tries to recycle the water using a decontamination system, which would remove radioactivity from the water in order to use it again for cooling purposes. But so far technical difficulties are reported.