Tokyo Electric Power Company has shown media its process of discharging treated and diluted water from the Fukushima Daiichi nuclear power plant into the sea.

TEPCO allowed access to its worksite to members of the press on Sunday, the fourth day of its water release.

Monitors in the room from which the equipment used for the discharge is remotely controlled show water levels in storage tanks.

A loud noise was heard outside the huge facility where the diluted water is stored, which suggests that the water is flowing into an undersea tunnel on its way to being released into the ocean.

TEPCO said it had released 1,420 tons of water by 5 p.m. Sunday.

It also said its equipment has been functioning normally, and seawater samples show no abnormality in radiation levels.

The company said it expects to discharge 7,800 tons of water by around September 10 as planned, equivalent to 8 tanks. More than 1,000 tanks at the plant are now used to store treated water.

The Fukushima Daiichi plant suffered a triple meltdown in the 2011 earthquake and tsunami. Since then, water used to cool molten fuel at the plant has been mixing with rain and groundwater.

The accumulated water is being treated to remove most radioactive substances, but still contains tritium. Before the release, the operator is diluting the treated water to reduce tritium levels to about one-seventh of the World Health Organization's guidelines for drinking water.