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Japanese government has reportedly issued a state of emergency plea after a cooling system failure at Fukushima Daiichi nuclear plant.

Japan's Nuclear Industrial Safety Agency has announced that a third explosion was heard early Tuesday morning at Fukushima Daiichi. The blast came from the building housing the No 2 reactor of the crippled nuclear plant, a breach of the containment vessel is feared.

Earlier on Monday Japan's government had confirmed that there were problems at the Fukushima Daiichi plant No.2 reactor. Chief Cabinet Secretary Yukio Edano said water levels at the reactor were falling.

A hydrogen explosion rocked the nuclear power plant earlier on Monday where authorities have been scrambling to avert a meltdown following Friday's massive earthquake and tsunami.

Technicians have been trying to cool reactors at the Fukushima Daiichi plant since Friday, following the earthquake and tsunami.

Meanwhile, the US has organized a delivery of coolant to the Japanese nuclear plant, according to Secretary of State Hillary Clinton. "We just had our Air Force assets in Japan transport some really important coolant to one of the nuclear plants," Clinton said.

The quake-damaged Fukushima nuke facility will vent its air containment vessels, as pressure levels have risen dangerously. The air may contain dangerous radiation, though an official evacuation notice for nearby residents has already been declared by officials.

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