TOKYO -- Approximately 5.5 tons of water containing radioactive materials have leaked from an equipment at Japan's Fukushima Daiichi nuclear power plant, local media reported Wednesday.

At about 8:53 am local time on Wednesday, workers discovered water leaking from the outlet of a device used to purify nuclear-contaminated water during the inspection of the equipment, Fukushima Central Television reported, citing the plant's operator Tokyo Electric Power Company (TEPCO).

TEPCO estimates that the amount of water that leaked was approximately 5.5 tons, which may contain 22 billion becquerels of radioactive materials such as cesium and strontium, the report said.

Most of the leaked water appeared to have seeped into the soil, but monitoring of a nearby drainage channel did not show any significant radiation level changes, it added.

TEPCO has made the area where the water was leaked a no-go area.

Hit by a 9.0-magnitude earthquake and an ensuing tsunami on March 11, 2011, the Fukushima nuclear plant suffered core meltdowns that released radiation, resulting in a level-7 nuclear accident, the highest on the International Nuclear and Radiological Event Scale.

The plant has been generating a massive amount of water tainted with radioactive substances from cooling down the nuclear fuel in the reactor buildings, which are now being stored in tanks at the nuclear plant.

In August 2023, Japan started to discharge the Fukushima wastewater into the Pacific Ocean, despite numerous and repeated objections by governments and communities, environmental groups, NGOs and anti-nuclear movements in Japan, neighbor countries and the Pacific region.