Indian officials say they will appeal for harsher sentences for seven former managers blamed for the 1984 gas leak that killed thousands of people in the central city of Bhopal.
The chief of India's central Madhya Pradesh state accused the federal government of failing to take "any serious steps" to get justice for victims of the leak.
Shivraj Singh Chouhan said he has created a panel of legal experts in order to appeal the case to India's High Court.
An Indian court Monday found seven top former managers at the now-defunct Union Carbide Company guilty of criminal negligence. The court sentenced them to two years in prison and ordered each to pay a fine of about $2,200.
The verdicts sparked outraged among relatives of the victims, who called the ruling "too little, too late."
The official death toll in the disaster at the Bhopal pesticide plant is 3,500 people. But activists say that over the years the poisonous gas leak has claimed more than 20,000 lives. Hundreds of thousands were either disabled or left grappling with chronic illnesses - ranging from kidney and liver damage, to cancer and birth defects.
Late Tuesday, victims and their relatives held a candlelight vigil in Bhopal City, promising they will not give up their fight for justice.
In 1989, Union Carbide paid a settlement of $470 million to the Indian government. The company was later bought by Dow Chemical, which said its legal liabilities ended with that settlement.
But disabled survivors say they have only received a small amount of the settlement money, and that the money they have received is not enough to pay medical bills and replace lost income.
Also Tuesday, Indian Law Minister Veerappa Moily said the government is still investigating the former top executive at Union Carbide, calling Warren Anderson a proclaimed offender.
Anderson was arrested after the gas leak but then left India. He now lives in the United States and has not answered court summons from India.
Some information for this report was provided by Reuters.