The central government and Kumamoto Prefecture said Tuesday they have appealed a lower court ruling that ordered them and a chemical company to compensate 128 unrecognized victims of Minamata disease, caused by poisoning with a form of mercury.

The Environment Ministry, which oversees the issue, said the appeal has been filed in part due to some points in the ruling differing from internationally recognized scientific knowledge of the disease and a finalized court decision.

The plaintiffs, who are aging, expressed their disappointment, saying they had hoped for immediate relief. The defense team said that six of the 128 plaintiffs will now appeal on the deadline, which is Wednesday.

Chemical company Chisso already filed an appeal last week.

In late September, the Osaka District Court ordered that the government, Kumamoto's prefectural authorities and Chisso pay a total of ¥350 million ($2.3 million) in damages to the victims, the first such ruling among similar lawsuits filed nationwide over the country's redress measure. The court had recognized that all of the plaintiffs in the lawsuit, who were not eligible for relief payments under a special law that went into force in 2009, were victims of Minamata disease.

The court also said it is possible to develop the disease even in areas and among age groups not covered under the 2009 special measures law, if individuals ingest methyl mercury by consuming large quantities of polluted seafood products.

Similar lawsuits are underway in Tokyo, Niigata and Kumamoto district courts, with the number of plaintiffs at more than 1,700.

The disease, formally acknowledged by local health authorities in 1956, was traced to mercury-contaminated water dumped into the sea by a Chisso chemical plant in the city of Minamata in Kumamoto Prefecture.

It was only in 1968 that the Japanese government recognized the disease was being caused by industrial pollution and stopped the water discharge.