Beijing (CNN) -- Earlier this week, the Jian River that runs through the city of Luoyang, Henan province in northern China, turned bloody red.
Local media started receiving panicky phone calls from citizens on Tuesday morning saying that the water of the Jian River near their neighborhood has become blood-like overnight.
The eerie sheen on the river lasted for nearly two days before local government officials managed to track down the source of pollutant: an illegal workshop dumping red dye into the city's storm water pipe network connecting the river.
Luoyang Municipal Environmental Protection Bureau cut off the workshop's power supply immediately and conducted a thorough examination, state-run Xinhua news agency reported.
Workers said on December 12 they had been rinsing a batch of red plastic bags for recycle but did not expect the consequences, Xinhua said.
The bags then were further traced back to nearby Mengjin County to a small chemical plant.The plant was accused of illegally producing red dye for firework wrappers preparing for the upcoming Chinese New Year.
Lab results from the Environmental Protection Bureau showed that despite the gruesome color, the "bloody water" contained no heavy metal or organic, poisonous elements.
The river has turned back to normal color on Thursday night, according to the Xinhua report.
But Luoyang residents said the Jian River changes color often because of the various pollutants and domestic garbage being dumped in or along it. Some even say they have seen it turn dark green.