Protesters camped outside an east China-based solar panel manufacturer accusing it of dumping toxic waste into a river.
The demonstration began on Thursday in the city of Haining.
Local media reported 500 people stormed a compound owned by Jinko Solar Holding Co before being dispersed by police.
Toxic waste from the factory killed large numbers of fish in a nearby river.
Authorities had already ordered the company to suspend operations, local media said.
Pollution has emerged as one of the biggest problems facing the Chinese government.
It is struggling to contain growing public anger against industries dumping toxic waste incorrectly.
Marie-Claire Fennessy, Reuters