The Radiological Protection Institute of Ireland has confirmed that it has detected the presence of trace amounts of radioactivity from the Fukushima accident in Ireland, but they are of no public health concern.

The amount of radio-iodine identified is extremely low, is consistent with levels found in other European countries and has no public health implications.

The sample was collected on the RPII's high volume air sampler which is located in Dublin and samples extremely large volumes of air.

The RPII's national monitoring network is used to provide an early warning of elevated radioactivity levels and the high volume air sampling system is the most sensitive element of this network.

Dr Ann McGarry, Chief Executive of the RPII, said: ‘The levels which have been identified are extremely low, are not a matter for concern and do not require any special actions to be taken.’

Meanwhile, Japanese Prime Minister Naoto Kan says his government is in a 'state of maximum alert' over the crisis at the crippled Fukushima nuclear plant.

He told a parliamentary committee meeting that the situation 'continues to be unpredictable'.

Radiation worries have disrupted efforts to restart the plant's cooling system, following the earthquake and tsunami on 11 March.

Plutonium found in the soil at the nuclear complex has heightened alarm in the area, and pressure is mounting on the prime minister to widen an evacuation zone around the plant.

Mr Kan said he was seeking advice on such a step, which would force 130,000 people to move in addition to 70,000 already displaced.

Plant operator Tokyo Electric Power Co said plutonium has been found 'at low-risk levels' in five places at the facility.

Japan's Nuclear and Industrial Safety Agency said while the plutonium levels were not harmful to human health, the discovery could mean the reactor's containment mechanism had been breached.

'Plutonium is a substance that's emitted when the temperature is high, and it's also heavy and so does not leak out easily,' agency deputy director Hidehiko Nishiyama told a news conference.

Dangerous conditions

Workers at Fukushima may have to struggle for weeks or months under extremely dangerous conditions to restart cooling systems vital to control the reactors and avert total meltdown.

Yesterday, highly contaminated water was found in concrete tunnels extending beyond one reactor, while at the weekend radiation hit 100,000 times over normal in water inside another.

That poses a major dilemma for Tokyo Electric, which wants to douse the reactors to cool them, but not worsen the radiation spread, said Chief Cabinet Secretary Yukio Edano.

'On the issue of pumping in water, we must avoid a situation in which the temperature (of fuel rods) rises and the water boils off.

'So this cooling is a priority. On the other hand, on the standing water, under the circumstances work must proceed to remove it as quickly as possible,' he said.

Japan says a partial meltdown of fuel rods inside reactor No 2 has contributed to the radiation levels.

The crisis, the worst nuclear accident since Chernobyl in 1986, has contaminated vegetables and milk from the area, as well as the surrounding sea. US experts say groundwater, reservoirs and the sea all face 'significant contamination'.