Tests have revealed that the dead pigs found floating on the Huangpu River in Shanghai died from porcine circovirus.
Shanghai Agriculture Committee wrote on its official microblog on Monday that the disease has been common in pigs in recent years.
Staff from the Shanghai Animal Diseases Control and Prevention Center collected five samples from the dead pigs, including their hearts, livers, spleens, lungs, lymph nodes and tonsils to test for viral pathogens.
The porcine circovirus will not affect humans.
Since Thursday, dozens of dead pigs have been found in the upper Songjiang section of the Huangpu River. Local departments soon began retrieving the pig carcasses and investigating the cause.
By Sunday, more than 1,200 pig carcasses had been retrieved.