Officials are still investigating the cause of the accident

Seven people were also injured, after steam leaked from a turbine at the Mihama plant in Fukui prefecture.

Officials insist that no radiation leaked from the plant, and there was no danger to the surrounding area.

An official from Japan's Nuclear and Industrial Safety Agency told news agency AFP that "about 10 people suffered burns" from the steam leak.

Kansai Electric Power Company, which operates the Mihama plant, said it had stopped power generation at 3:28pm (0628 GMT), and was still investigating the cause of the accident.

"Steam spewed in the turbine building area at the number three nuclear reactor," a spokesman for Kansai Electric Power said.

Officials said a lack of cooling water caused the accident, forcing steam to escape from the turbines.

The steam was at a temperature of 200C, according to media reports.

In the aftermath of the accident, no evacuation order was given to residents living near the plant, and city official Nobutake Masaki denied there was any danger to the surrounding area.

An official from Japan's Nuclear and Industrial Safety Agency told AFP that it would be impossible for the leaked steam to contain radioactivity, as the turbines did not come into contact with water used in the nuclear reactor.

Safety doubts

Japan relied on nuclear power to supply 25% of its electricity in 2003, according to figures from the UN's nuclear agency.

But a string of safety problems, including an accident in 1999 which killed two workers and affected hundreds of others in Tokaimura, north-east of Tokyo, has undermined public confidence.

At Mihama itself, a leak of cooling water from the number two reactor in 1991 spurred a Japanese campaign against building further reactors.

Our correspondent in Tokyo, Jonathan Head, says questions will again be raised about the safety of nuclear power in Japan.