SNAPSHOT-Japan's nuclear crisis

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TOKYO, March 21 (Reuters) - Following are main developments after a massive earthquake and tsunami devastated northeast Japan and crippled a nuclear power station, raising the risk of uncontrolled radiation.
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- The World Health Organisation says the detection of radiation in food is a more serious problem than first expected, and food contamination is not a localised problem. It says, however, there is no evidence of contaminated food from Fukushima reaching other countries.
- The operator of the stricken Fukushima plant said a small trace of radiation had been found in the Pacific sea waters nearby, but officials stressed the levels were minute and posed no immediate danger.
- China and South Korea say they will toughen radioactivity tests on imports of Japanese food, and Japan tells four prefectures near the nuclear plant to halt shipments of spinach.
- Government also bans milk shipments from Fukushima province.
- Government says Japanese food produced outside the nuclear crisis zone is safe.
- Official death toll from earthquake and tsunami 8,450 with 12,931 missing. Police say more than 15,000 feared dead in Miyagi prefecture alone.
- The U.N. atomic agency chief said on Monday that Japan's nuclear situation remained very serious but that he had no doubt the country would "effectively overcome" the crisis.
- Japan's nuclear safety agency says it sees risk of radioactive dust being inhaled by workers at Fukushima Daiichi nuclear power plant, but there are no signs that has happened yet.
- Reactors at the Daiichi nuclear power plant are showing some improvement but the situation remains uncertain, Tetsuro Fukuyama, Japan's deputy chief cabinet secretary, says.
- Firefighters postponed spraying Japan's badly damaged nuclear reactor No. 3 with seawater on Monday after a plume of grey smoke was seen over the structure, the government says.
* Engineers have re-established power cables to all six reactors. Electricity restored at No. 2 reactor and a pump in reactor No. 5 is now running on power from grid. The No. 1 reactor is able to receive power from the grid.
- If engineers are unable to cool the reactor, the last option would be entombing the plant with concrete and sand to prevent a catastrophic radiation leak, the method used at Chernobyl in Ukraine in 1986.
- Tests detect radiation above the national safety level in spinach and milk produced near the Fukushima plant. A sample of tap water from Tokyo shows a tiny level of radioactive.

- The health ministry said that radiation levels exceeded safety standards in Fukushima and nearby Ibaraki prefecture. It said it had prohibited the sale of raw milk from Fukushima prefecture.
- The earthquake and tsunami will depress growth briefly before reconstruction kicks off and gives the beleaguered economy a boost, the World Bank says in a report.
(Tokyo bureau; Compiled by World Desk Asia)