Radiation has leaked from Japan’s Fukushima nuclear power plant it appears, after radioactive contamination was found in the water and soil around the plant.

Elevated levels of radioactivity have been found in the ocean close to Fukushima, officials say.

Plutonium has also been found in soil at the plant, although apparently not at levels that threaten human health.

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Plant operator Tokyo Electric Power Co (Tepco ) said that it was not clear where the plutonium has come from, but confirmed that teams are still working around the clock to contain the disaster.

According to experts, the plutonium probably came from spent fuel rods stored in pools at the plant. On March 11, the earthquake and tsunami damaged the pools and exposed the rods, which subsequently heated up beyond safe temperature levels.

Another explanation is that the plutonium may be leaking from Fukushima’s reactor No. 3, the only one at the plant that uses the element.

Radioactive water had previously only been found within the nuclear plant itself, however contamination has now been found in an underground maintenance tunnel, with one end located about 55m from the shore.

Radiation levels in the water measure 1,000 millisieverts an hour, a dose high enough cause temporary radiation sickness.

Plutonium has also been detected in soil at five locations at the plant but not at levels that represented a risk to human health, Tepco said.

Tepco came under fire at the weekend for mistakenly announcing on Sunday that a highly radioactive pool of water in the No 2 reactor was 100 times more radioactive than it actually was.

Japan’s Nuclear and Industrial Safety Agency has vowed to increase monitoring in the plant and beyond the 12-mile exclusion zone imposed by the government around Fukushima.