A fabric printing company in Pudong New Area will be punished for discharging wastewater into a nearby river, turning the water blue, the Pudong New Area Environmental Protection Bureau said Wednesday.

The bureau began looking into the company Tuesday afternoon after residents of Hangtou town reported that the river had turned blue the previous day, according to a report in the Xinmin Evening News.

Authorities identified Shanghai Yiming Fabric Printing Co as the source of the wastewater, though they have not yet identified what pollutants have contaminated the river, said Sun Shengnan, an official for the Pudong New Area Environmental Protection Bureau.

The company's factory is located in the Damai Bay Industrial Zone, which is adjacent to the river that flows through the town, the report said.

The factory released the wastewater into the storm sewer system, which is how it ended up in the river, Sun told the Global Times.

The authorities have not determined the factory's punishment. Any fine issued will hinge on what kind of pollutants ended up in the river.

Accounts from residents and officials show the river is no stranger to pollution.

It was contaminated last year after factories in the industrial zone discharged sewage into the storm sewer system, which is only supposed to be used for drainage, said an official surnamed Wang with the township government.

A town resident said that the river reeks of sewage after it rains, the Xinmin Evening News reported. The river water sometimes even turns white or black. "Although residents no longer drink from the river, they still worry that the colored water will damage their health," Wang told the Global Times.

The authorities will prevent factories from discharging pollutants into the river and will punish those that disobey the rules, Wang added.