Fire has again broken out at the quake-stricken Fukushima Daiichi nuclear plant in northern Japan.
The new blaze began at reactor four. The plant has already been hit by four explosions, triggering radiation leaks and sparking health concerns.
More than 3,000 have been confirmed dead and thousands are missing following Friday's 9.0-magnitude quake and tsunami in north-east Japan.
The disaster has damaged the nuclear plant's cooling functions.
Officials have warned people within 20-30km (12-19 miles) of the site to either leave the area or stay indoors.
The Tokyo Electric Power Co, which operates the Fukushima plant, said on Wednesday that efforts were under way to put out the latest fire.
The crisis at the plant - which contains six nuclear reactors - has worsened since 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, while a fourth damaged the building of reactor four, where a fire also broke out in the unit's spent fuel storage pond.
Reactor four had been shut down before the quake for maintenance, but its spent nuclear fuel rods were still stored on the site.
Officials said the explosions at the first three reactors, and possibly the fourth as well, were caused by a buildup of hydrogen.
Chief Cabinet Secretary Yukio Edano said officials were closely watching the remaining two reactors, as they had begun overheating slightly.
He said cooling seawater was being pumped into reactors one and three - which were returning to normal - and into reactor two, which remained unstable.
The repeated releases of different amounts of radiation - some large, some small - are unnerving the Japanese and their neighbours, who want reassurances that the situation will soon be brought under control, says the BBC's Chris Hogg in Tokyo.
Japan's nuclear safety agency said earlier it suspected the blast may have damaged reactor two's suppression chamber, which would have allowed radioactive steam to escape.
Further strong aftershocks continue to rock the country. An earthquake, not considered an aftershock, of magnitude 6.2 centred south-west of Tokyo shook buildings in the capital late on Tuesday.
http://www.bbc.co.uk/news/world-asia-pacific-12754883