China's environment ministry has ordered an investigation after a provincial environmental protection body fined a polluting factory just 603 yuan (US$90 or S$122) for dumping waste water, state media said on Friday.
China's government has repeatedly vowed to get tough on pollution, which has fouled the country's air, soil and water, prompting public ire.
But enforcement of laws is often lax.
The official Xinhua news agency said the chemical plant in Gaoyou city in the eastern province of Jiangsu was given the fine for dumping water with an abnormal pH level.
"After the news was released it was called into question by the public, who thought a fine of 603 yuan was too low and insufficient to act as a deterrent to companies which break the law on the environment," Xinhua said.
The environment ministry was paying "great attention" to this case and had ordered an investigation and for "serious punishments" to be meted out, the report added.
Environmental protection bodies at all levels had a responsibility to uphold the law, the ministry added.