Both explosions were probably caused by a build-up of hydrogen gas. A third reactor at the complex has reportedly lost its cooling system.

The Japanese authorities have been struggling to prevent a meltdown of two overheating reactors at the aging Fukushima plant after the cooling systems were damaged in Friday’s 8.9-magnitude quake and the resulting tsunami.

The chief government spokesman Yukio Edano said that the number three reactor was probably undamaged and there was a low possibility of a major radiation leak at the plant, 250 kilometers northeast of Tokyo.

**”Partial meltdown”**
Edano said on Sunday it was likely a partial meltdown had occurred at the Fukushima number-one reactor. A meltdown occurs when a reactor core overheats and causes damage to the facility, potentially unleashing radiation into the environment.

France’s Institute of Radiation Protection and Nuclear Safety said *”very large”* amounts of radioactivity were *”produced simultaneously with the explosion”* at Fukushima on Saturday. A total of 210,000 people living near the two Fukushima nuclear plants have been evacuated.

Japan relies on nuclear energy for about a third of its power needs. Rolling power outages were due to start later on Monday. Millions of people have already been without electricity since the disaster hit on Friday, forcing the shutdown of nuclear plants in the affected areas.

**Relief effort**
Prime Minister Naoto Kan said in a televised national address on Sunday that Japan was facing its worst crisis since the end of World War II — which left the defeated country in ruins. The death toll in the 9.0-magnitude earthquake is expected to exceed 10,000, and the economic damage is estimated at between 10 billion to 25 billion euros. Japan has committed 100,000 troops – about 40 percent of its armed forces – to relief efforts as many survivors are left without water, electricity, fuel or enough food.

Japan sits on the *”Pacific Ring of Fire”*, and Tokyo is in one of its most dangerous areas, where three continental plates are slowly grinding against each other, building up enormous seismic pressure. The US Geological Survey said that the immense force of Friday’s quake has moved Honshu – the main Japanese island – by 2.4 meters.