A court on Monday found the Indian unit of U.S. chemicals firm Union Carbide and seven Indian employees guilty of negligence over one of the world's worst industrial accidents that killed thousands of people in 1984.

Union Carbide plant in the central city of Bhopal accidentally released toxic gases into the air and the government says around 3,500 people died as a result. Activists say 25,000 died in the immediate aftermath and the years that followed. The verdict is the first in more than 25 years that could lead to jail sentences of up to two years and fines for those convicted, though rights activists said the punishment would be too light.

Keshub Mahindra, current chairman of India's top utility vehicle and tractor maker Mahindra & Mahindra, was the highest ranking person convicted on Monday. He was chairman of Union Carbide India Ltd, a unit of Union Carbide, at the time of the accident. Union Carbide's Indian arm was also found guilty. Those convicted can appeal to a higher court, a process that in India can take years. "It's actually going to be nothing. What is it? We're looking at maximum punishment of two years or a fine. If that's not the biggest joke, then I don't know what is," Rachna Dhingra, a Bhopal rights activist, told Reuters. "There's nothing to be happy about."

The verdict in Bhopal applied only to Indian officials of the former Union Carbide's Indian arm while separate cases have been filed against the company and its overseas officials. Union Carbide had settled its liabilities to the Indian government in 1989 before being bought over by Dow Chemical.