Water containing radioactive materials has leaked from a caesium absorption tower at the Fukushima-Daiichi nuclear power station in Japan, the International Atomic Energy Agency said.

The estimated 5.5 cubic metres of water was assessed to have leaked from a valve left open during cleaning work at the absorption tower.

The leaked water was from the system filtering water as part of the decommissioning activities at the site. The event is not related to the discharge of the treated water into the ocean.

The IAEA said Fukushima-Daiichi owner and operator Japan’s Tokyo Electric Power Company (Tepco) told it about the leak on 7 February.