A second explosion has taken place at Japan’s Fukushima nuclear plant, three days after the earthquake hit, damaging the cooling system of the 40-year-old nuclear reactor.

Scientists and technicians have been battling to control two overheating reactors at the Fukushima Daiichi nuclear facility. However today the No. 3 reactor – which has been under emergency watch – exploded injuring ten people.

The blast of the latest explosion at the nuclear plant was felt 25 miles away and came soon after Japan’s Prime Minister Naoto Kan appeared on television telling the nation that the plant was in an “alarming” state.

Six workers at the nuclear plant and four soldiers were hurt in the blast.

Japan’s government is trying to allay fears of a catastrophic radiation leak, saying the reactor’s inner containment vessel – which contains the nuclear fuel – is still intact.

Following the latest explosion Japan’s Chief Cabinet Secretary Yukio Edano said: “The soundness of the reactor container has been maintained. The figures do not indicate a high level of radiation.”

However people within a 20km (12 mile) radius were being ordered to stay inside.

The blast was caused by a build up of hydrogen, the same thing that led to an explosion on Saturday which blew apart the building surrounding the plant’s No. 1 reactor.

A total of 22 people were confirmed to have suffered radiation contamination following Saturday’s blast, while up to 190 may have been exposed.

Australians caught in earthquake-hit Japan

Officials have been battling to prevent multiple nuclear reactor meltdowns after the devastating quake and tsunami incapacitated the Fukushima plant.

Seawater is being used in a desperate attempt to cool them amid fears that radioactive material could escape into the air with devastating consequences.

More than 180,000 people have evacuated the area.

The nuclear crisis was triggered by a 9.0 magnitude earthquake followed by a tsunami that hit Japan’s north-eastern coast on Friday.

More than 1,400 people were killed, but a police chief said the death toll may be over 10,000.

Prime Minister Naoto Kan said the disaster was the biggest crisis Japan has faced since World War Two.