Protesters gathered outside the plant in Bhopal, burning effigies of former Union Carbide chairman Warren Anderson. They also demanded his extradition from the U.S. to face trial in India.
An effigy of India's prime minister was also burned, with the group blaming the government for not doing enough to get money for victims.
Union Carbide paid India $470 million in an out-of-court settlement 14 years ago in exchange for charges against both the company and Anderson being dropped. India's Supreme Court reinstated the charges 12 years ago, but India has never aggressively pursued Anderson's extradition.