According to the plant's operator, Tokyo Electric Power Company (TEPCO), the trouble could have been caused by faulty filters.
One of the three lines of the Advanced Liquid Processing System (ALPS) was turned off after the engineers found out that the water contains calcium, hindering the elimination of radioactive strontium.
Since March, the ALPS system at Fukushima has had a series of similar failures. TEPCO then replaced the filters and resumed the system operations, highlighting company's plans to set up another facility to treat the tainted water.
On March 11, 2011, the Fukushima nuclear power plant was hit by a powerful earthquake and a subsequent tsunami, which caused a partial meltdown of three of the plant's nuclear reactors as radiation leaked into the atmosphere, soil and sea.
The incident was the world's worst nuclear disaster since the 1986 Chernobyl catastrophe.
Several areas within the 20-kilometer (12 miles) zone from the plant are still considered unfit for habitation due to the high levels of radioactive contamination.
TEPCO has been widely criticized for being inadequately prepared for a tsunami and for its slow response to the disaster.
Cleaning the toxic waste from the abandoned nuclear plant and reactors decommissioning have become the principal task of TEPCO, the process of disaster cleanup is expected to take at least 40 years.
Source: RIA Novosti