Minamata was the site of Japan's worst ever industrial poisoning and is regarded as the dark side of Japan's rapid modernisation during the 20th Century.

For decades, a synthetic resin factory run by chemical company Chisso Corp had been dumping methylmercury into the bay of the town on southwestern Kyushu island, poisoning the marine habitat.

The methylmercury accumulated in shellfish and fish in the bay. For the many people living nearby whose chief source of protein was the sea, it meant the gradual build-up in their bodies of this powerful toxin.

Victims suffered spasms, seizures and loss of sensation and motor control that impaired their ability to walk and speak. Babies were born with nervous system damage and other mental and physical deformities.

The health problems and mysterious deaths of humans and animals were reported in the fishing communities of Minamata in the early 1950s, but no action was taken.

The first official report by a local hospital came in 1956. Although Chisso was immediately suspected, its management denied responsibility and the plant continued dumping mercury until 1968, when it was officially blamed for the health problems.

In the 12 years that separated the two events, estimates suggest as much as 150 tonnes of mercury was discharged by the factory, sickening many more people.

Documents published on the Ministry of the Environment's website say fears over the impact on Japan's soaring economy were to blame for the long delay in tackling industry over environmental standards.

Around 2,000 of those affected by the mercury poisoning have now died, many thousands more are still suffering its effects.

In 2009, more than half a century after the first case was officially reported, the Japanese government created a special law to compensate victims of what had become known as "Minamata Disease".

More than 65,000 people applied for redress over the following three years, while plaintiffs seeking compensation from Chisso and the central and local governments reached out-of-court settlements.

The outbreak of Minamata Disease is considered a turning point in Japan for awareness of the environmental and human cost of unfettered economic development and led to the gradual introduction of safeguards.