Workers have returned to a stricken Japanese nuclear plant after a rise in radiation levels forced them to temporarily abandon the facility.
Earlier, a blaze struck reactor four at Fukushima Daiichi for the second time in two days, and smoke was seen billowing from reactor three.
Friday’s 9.0-magnitude earthquake and tsunami, which killed thousands, damaged the plant’s cooling functions.
The site has been hit by several explosions, triggering radiation leaks.
However, the 50 technicians were later allowed to return to the facility, located 220 kilometres north of Tokyo.
Authorities pulled out 750 workers on Tuesday, leaving a skeleton crew trying to cool the plant’s four reactors and avert a meltdown.
The new fire at reactor four was reported early on Wednesday. Three hours later, Japan’s nuclear safety agency said flames could no longer be seen.
On Tuesday morning, another fire broke out in the spent fuel storage pond at reactor four.
The reactor had been shut down before the quake for maintenance, but its spent fuel rods are still stored on the site.
Kyodo news agency says the storage pool may be boiling and further radiation leaks are feared.
The Tokyo Electric Power Co (Tepco), which operates the Fukushima plant, said it may pour water and fire retardant from helicopters to stop fuel rods from being exposed to the air and releasing even more radioactivity.
The crisis at the plant – which has six nuclear reactors – began when the earthquake struck. Explosions rocked the buildings housing reactors one and three on Saturday and Monday.
On Tuesday morning, a third blast hit the building of reactor two.
Officials say the explosions at the first three reactors, and possibly the fourth as well, were caused by a buildup of hydrogen.
People living within 20-30 kilometres of the site have been told to either leave the area or stay indoors.
More than 3,300 people have been confirmed dead and thousands are missing after Friday’s quake and tsunami.
In the north-eastern town of Otsuchi, the fate of half of the population – around about 8,000 people – remains unknown.
More than 500,000 people have been made homeless by the quake and tsunami. Many are enduring snow and freezing temperatures, as supplies begin to reach the worst affected areas.
The government has deployed 100,000 troops to lead the aid effort and the army is also using helicopters to bring in basic supplies.
Strong aftershocks continue to rock the country. A 6.0 magnitude tremor struck in the Pacific just off Chiba prefecture, east of Tokyo, on Wednesday.
On the Tokyo stock exchange, the Nikkei index ended the day up more than 5%, recovering some ground after plummeting about 17% over the two days.