A second explosion has occurred at the Fukushima Daiichi atomic power plant in quake-hit Japan, officials have confirmed.

The blast follows a similar explosion at the No. 1 reactor, which occurred after hydrogen ignited when it mixed with oxygen.

Three workers have been injured and seven are missing, according to the Tokyo Electric Power Company, the owner of the plant.

At present, there are no indications of increase in radiation levels around the plant, and while the wall of the building housing the No. 3 reactor collapsed in the explosion today, officials state that there is low possibility of a radiation leak.

As a precautionary measure, some 170,000 residents living within a 20km radius of the plant have been asked to remain indoors.

Currently, 11 of the 50 nuclear reactors in Japan in areas worst affected by the earthquake have been shut down, an action that is estimated to reduce the country’s output from nuclear power by 25% to 50%.

The earthquake of 9.0 on Richter scale hit Japan on 11 March and triggered a tsunami, causing huge damage to life and property in the country.