Tokyo Electric Power Co said Wednesday it had suspended a radioactive water treatment system at the Fukushima Daiichi nuclear plant due to deteriorating performance. The operator found Tuesday that one of the three lines in the cleanup system did not eliminate radioactive material sufficiently.

Tokyo Electric halted all three lines called the Advanced Liquid Processing System (ALPS), but it did not detect any defects in the other two, said Akitsuka Kobayashi, a company spokesman.

The operator has been investigating the problem since Tuesday, Kobayashi said.

The system is regarded as a key facility to deal with the massive amounts of radioactive water at the Fukushima Daiichi Nuclear Power Station as the operator continues to inject water into three of its six reactors to keep them cool.

The plant suffered meltdowns at the three units after a tsunami swept through the complex in March 2011.

In February, the operator started the three ALPS lines simultaneously on a trial basis, but the system has encountered a series of problems.

If all the lines operated fully, about 750 tons of toxic water could be treated every day, Kobayashi said.