Smoke and explosion have been seen No.3 reactor of Fukushima No.1 nuclear power plant, AFP reported on Sunday.
According to Japan’s nuclear safety agency, the blast was believed to be caused by hydrogen.
“We believe it was a hydrogen explosion. It is not immediately known if it affected the reactor,” said spokesman Ryo Miyake.
On Saturday, Fukushima Daiichi 1 nuclear reactor started oozing radioactive radiation after a blast that blew the roof off the plant, which was hit-hard by the massive 8.9 magnitude earthquake that struck off the northeast coast of Japan’s main island a day earlier.
Operators had earlier halted injection of sea water into the reactor, resulting in a rise in radiation levels and pressure.
The government had warned that an explosion was possible because of the buildup of hydrogen in the building housing the reactor