Japan put its top priority on Wednesday on efforts to cool down a plutonium-fuelled nuclear reactor, attempting at one stage to water-bomb the facility without success amid fears that authorities were running out of options to avert disaster.
The No.3 reactor is the only one of the quake-stricken Fukushima Daiichi plant's six reactor units to be powered with plutonium, which is far more hazardous to health than uranium, which is used to power the other five reactors.
High radiation levels had stopped a military helicopter from dumping water on the No.3 reactor, local media said. The plant's owner, Tokyo Electric Power , declined to comment.
It was not clear if the helicopter was trying to pour water on the reactor vessel or on an associated spent-fuel pool, a deep reservoir where spent nuclear fuel rods are kept. Public broadcaster NHK said the water was for the spent-fuel pool.
Later, Kyodo news agency quoted a government taskforce as saying it was unlikely the No.3 reactor had sustained major damage.
The number of workers at the complex has increased to 180, up from 50 a day earlier but still far less than the 800 that were deployed there immediately after Friday's devastating 9.0 magnitude quake and tsunami.
Debris on roads has hampering efforts to bring in equipment, and there are plans to bulldoze a road into another part of the complex, the No.4 reactor, which is the second priority.
"The situation at the No.4 reactor is not exactly a good situation but the No.3 reactor is a higher priority," a Tokyo Electric Power official told a media briefing.
On Tuesday, an explosion blew two holes in the wall of a building housing the No.4 reactor unit's spent-fuel pool, exposing it to the atmosphere.
Tokyo Electric also said it was not sure what was happening at the No.2 reactor, which saw a sudden drop in pressure.
The company said this might indicate it was being cooled or it could also be an ominous sign that there was a hole in the core container. Or it might just be a faulty pressure reading.
"We cannot with certainty say whether or not the core container is airtight," the company official said.
The company also said it was pouring water at the reactors No.5 and No. 6, but it was also not immediately clear into which parts of those two reactor units.
It did say, however, that temperatures at the spent-fuel pools in those reactors had risen slightly since Wednesday morning. There was water in the pools but it was having trouble circulating the water because of cooling-system problems.
There was no new data on temperatures of the spent- fuel pools at reactors No.1 to No.4.
Officials said the strikes began in the last week and were against extremist targets in the southern part of the country.
The poll comes as Australia attempts to rebalance its economy away from a once-in-a-generation mining boom stymied by tumbling commodities prices.
More than 840 others injured after extreme weather conditions battered eastern city of Yangcheng
Driver detained after bus carrying 56 people bursts into flames after crashing into guardrails of highway in central Hunan
Philippine army says 7 sailors abducted earlier this week handed over by kidnap-for-ransom gang to ISIL-linked militants
Blast damages several roadside vending stalls, shatters windows of nearby buildings including a school
Jailed opposition leader says parties must end internal disputes if they are to offer strong alternative to ruling alliance
North Sumatran capital of Medan teaches blind students love of Islamic holy book through braille
The Chinese government has announced it halted a communication channel with Taiwan due to the self-ruled island's refusal to recognise recognise "one China" principle with tensions rising between the two governments.
An increased amount of police has been deployed to majority Buddhist town after mob destroys mosque, religious school and Muslim cemetery
The Shangri La dialogue at the beginning of the month showed a US push towards creating a second Asian flavoured NATO
Mobs of people have burnt down a mosque and looted shops in apparent reprisal for an attack on three Zimbabweans on Tuesday, which left one man dead, while a second man died in hospital on Thursday afternoon.
Former deputy premier and ex-state chief had shared opposition stage to condemn PM and government
Says her new government 'understands we have to create an environment where our people want to return'
Sam Rainsy in self-imposed exile in US after warrant for his arrest issued stemming from years-old defamation case
US President Barack Obama said Mansour was targeted because he was an obstacle to the peace process