Explosion destroys walls of Japanese NPP Fukushima-1

The Economy, Trade and Industry Ministry's Nuclear and Industrial Safety Agency said Saturday afternoon that a nuclear meltdown was suspected at the Fukushima No. 1 nuclear power plant's No. 1 reactor.

An explosion was heard from the No. 1 plant at about 3:36 p.m. and white smoke was witnessed about 10 minutes later, Tokyo Electric Power Co officials said, adding that four workers were injured. However, the cause of the blast remained unknown, according to The Daily Yomiuri.

Fuel rods at the No. 1 reactor at the plant run by Tokyo Electric Power Co. may be melting after radioactive Cesium material left by atomic fission was detected near the site, Nuclear and Industrial Safety Agency, spokesman Yuji Kakizaki said by phone today.

"If the fuel rods are melting and this continues, a reactor meltdown is possible," Kakizaki said. A meltdown refers to a heat buildup in the core of such an intensity it melts the floor of the reactor containment housing, Bloomberg reports.

Japanese TV began warning people living near Fukushima nuclear power station to stay indoors. Residents were being told to turn off air-conditioners and not to drink tap water. People going outside were also been told to aviod exposing their skin and to cover their faces with masks and wet towels.

Prime minister Naoto Kan had earlier warned that a radiation leak might occur at one of the reactors at the Daiichi facility at Fukushima, which is close to the stretch of coast that took the full force of the tsunami triggered by Friday's 8.9-magnitude quake, Telegraph.co.uk says.