6.45pm Agence France Presse reports that No radiation leaks have been detected from Japan's nuclear power stations after the quake.
11.22pm More detail from The Associated Press on the state of emergency issued at a nuclear plant after its cooling system failed:
Chief cabinet secretary Yukio Edano says the nuclear power plant in Fukushima developed a mechanical failure in the system needed to cool the reactor after it was shut down in Friday's earthquake.
He said the measure was a precaution and there was no radiation leak at the Fukushima No. 1 power plant. He said the facility was not in immediate danger.
11.31pm Some 2,000 residents living near Japan's Fukushima nuclear plant have been urged to evacuate.
3.40am Reports indicate the situation at the Fukushima Daiichi nuclear plant is "under control". The World Nuclear Association has said it understands that water is now being pumped into its cooling system. Reuters has also reported the US has transported emergency coolant to the plant. US Secretary of State Hillary Clinton said:
We just had our Air Force assets in Japan transport some really important coolant to one of the nuclear plants. You know Japan is very reliant on nuclear power and they have very high engineering standards, but one of their plants came under a lot of stress with the earthquake and didn't have enough coolant.
5.44am BBC quotes nuclear physicist Dr Walt Patterson as saying the situation at the Fukushima-Daiichi plant is "the sort of thing that nuclear engineers have nightmares about ... if it is not resolved in the next few hours it will get serious". Read their analysis of the nuclear emergency.
6.02am The situation at the nuclear power plant appears to be worsening, The Associated Press has quoted an anonymous official as saying if the outage in the cooling system persists, eventually radiation could leak out into the environment, and, in the worst case, could cause a reactor meltdown. However the Guardian mentions a nuclear expert speaking to CNN has said this was only a remote possibility.
6:50am The Japanese government has declared an atomic emergency and told thousands of residents living near a nuclear plant in Fukushima to evacuate, warning a small amount of radiation could be released, AFP reports.
8:48am Radiation levels at the damaged Fukushima-Daiichi nuclear plant are continuing to rise. The Jiji Press news agency says the levels are eight times above normal, BBC reports.
9.27am Japan says radiation levels have surged outside nuclear plant, expands area subject to evacuation, The Guardian reports.
9.44am Japan's public broadcaster NHK, quoting nuclear safety officials, said there was "no immediate health hazard" to nearby residents from a possible minute leakage at the Fukushima No1 nuclear power plant.
9.46am Japan's nuclear safety agency has confirmed the damaged Fukushima No 1 has been leaking radiation outside the plant, the Guardian.co.uk reports. According to the Guardian, there are now also reports from nuclear plant operator Tepco that the Fukushima No 2 plant has lost cooling to three of its reactors.
10.51am Japan's nuclear safety agency is reportedly set to issue an unprecedented order for Tepco to open a valve at the damaged Fukushima nuclear power plant to release pressure, according to the Guardian.co.uk.
11.22am According to Al Jazeera, there are now five reactors under a state of emergency - two at Fukushima No 1 (Daiichi) plant, and three at the nearby Fukushima No 2 (Daini) plant.
11.44am Japan's trade ministry has announced that Fukushima's plant operator Tepco is "considering releasing pressure" at the Fukushima No 2 (Daini) nuclear plant, according to the Guardian.co.uk. The Government has also just ordered the evacuation of a three kilometre radius around the plant.
12.04pm The Japanese Government is currently holding an emergency meeting on the subject of the Fukushima nuclear plants, according to the Guardian.co.uk.
Not good.
Also,
12.20pm Japan's quake caused the day to become a bit shorter. NASA geophysicist Richard Gross calculated that Earth's rotation sped up by 1.6 microseconds, according to an Al Jazeera report, which cited AP.
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