An emergency operation has been launched to clean a river after a worker dumped pigs' blood in the water in Changsha, Hunan province, thepaper.cn reported on Tuesday.

The suspect, a driver from a cleaning service company surnamed He, has been detained for illegally discharging pig's blood into the sewer, turning the river red.

A director of local environmental protection bureau said the driver carried pigs' blood from a slaughtering market and discharged it into the sewer nearby.

A livestreaming video released on Sunday showed the polluted water flowing into the river, turning the river red with white foam floating on the water. The feed also showed that the process lasted a whole day.

On Sunday evening, the pollution source was cut off. The case is under investigation.

Zheng Yumeng contributed to this story