The Shanghai government on Friday launched an investigation into a case of illegal dumping of chemical waste that caused severe air and river pollution in suburban Jinshan and Songjiang districts.

Residents in Zhujing town, Jinshan district, and the adjacent Maogang town of Songjiang district reported a pungent odor to local authorities at 7:40 pm Thursday.

"I realized there was a smell at around 7:30 pm that covered the whole town.  You could smell it even with your windows shut," a resident in Zhujing surnamed Jiang told the Global Times Friday.

Local authorities later found chemicals including styrene in the waters of Jueshi Port. Authorities began to monitor air and water quality in the two districts every two hours, and tested water quality on an hourly basis, according to the Jinshan district government.

The cause of the incident was illegal dumping by a tank truck from a local logistics company, and police have detained at least 10 people who may have been involved in the case, the municipal government said Friday morning.

Sixty cleaning vessels were dispatched to clean up the floating chemicals. A dam on the Huangpu River was also shut to prevent the pollutants from spreading.

A water plant in Songjiang was closed down to prevent possible pollution, and nine fire engines were dispatched to supply water to the affected areas, which include eight villages and a neighborhood community. Jinshan district, where water supply was said to be still normal, has also set up four locations to supply residents with bottled water.

Doctors in Jinshan were asked to be on standby at 2 am Friday to treat patients with possible respiratory problems, and neighborhood community staffers were sent to visit families with elderly people and children to see if there were any poisoning cases, but no such case had been found as of Friday afternoon, the Jinshan government said.

Residents also took various measures to protect themselves.

The mother of a 4-month-old baby, surnamed Wang, told the Global Times that she would leave the district for several days.

"It would be better if the government could inform us of exactly what kind of chemical it is and how harmful it is to people," Jiang said.

He added that he had bought five barrels of drinking water for the coming days.