As the first pictures of the 'Fukushima 50' emergency crew emerge, the hailed workers have resumed work at the plant a day after a plume of dark smoke forced them to evacuate.
Using fire engines, high-pressure water jets are aimed at the quake-hit and charred nuclear reactor in Japan.
Workers have struggled to avert a meltdown at the Fukushima plant northeast of Tokyo that has belched radiation, forcing tens of thousands to evacuate, contaminating farm produce and drinking water, and sparking wide anxiety.
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White steam was seen rising from four of the six reactors.
Workers had been pulled back after dark smoke rose from the number three reactor unit, which was badly hit by the massive 9.0-magnitude earthquake and towering tsunami which battered northeast Japan on March 11.
The quake severed external power to the plant. Reactors one to three, which were operating at the time, automatically shut down but the tsunami knocked out the backup generators and the cooling systems failed.
Early on Thursday the Tokyo fire department engines again aimed their powerful seawater jets at the site to top up a spent fuel pool inside the unit.
The focus is on the number three reactor, of special concern since it uses volatile uranium-plutonium fuel.
Retopping the containment pool aims to stop it from being exposed to air where it could release large-scale radiation.
Engineers have now linked up an external electricity supply to all six reactors and are testing system components and equipment in an effort to soon restart the cooling systems and stabilise the reactors.
Power has been partially restored to the control room of the number three unit. Previously workers had to grope around in the dark, using flashlights, without an air-conditioning system to extract elevated radiation.
The plant is located 250 kilometres northeast of Tokyo.
The government has declared an exclusion zone with a radius of 20 kilometres around the power station and evacuated tens of thousands of people, while telling those within 20 to 30 kilometres to stay indoors.
