The Tokyo Electric Power Company is looking into why a system for decontaminating radioactive water at the Fukushima Daiichi plant is not working as expected, delaying resumption of the system's full-scale operation.

The firm on Wednesday published data showing the amount of radioactive materials that had been removed from contaminated water during a test run of the US-made system.

The data show that density of Cesium-13 and Cesium-137 dropped to only one-100th of initial levels.

An earlier test run using water with a lower density of radioactivity showed a drop to about one-1000th.