Authorities have launched an investigation into a sewage discharge in three industrial parks in Lianyungang, Jiangsu province, the provincial environmental protection bureau said on Thursday.

The discharges occurred in the city's Guanyun county. Monitoring, supervisory and law enforcement experts gathered in Lianyungang to address the environmental situation, with results to be announced later.

The issue was first brought to light by China Central Television on Wednesday in a report showing a layer of white foam clogging many farmland ditches. The sewage, locals claim, was released into the Guanhe River through "illegal underground pipes" from nearby factories.

At the Yangshanhua factory, for example, a valve was installed on a sewage discharge pipe linking the plant's sewage treatment pond to a central sewage treatment facility in an adjacent industrial park. When the valve opens, sewage is routed into the treatment plant, but when it is closed, the sewage runs directly into the river through "secret pipes".

Residents said the pipes were used to save factories sewage treatment expenses. Also in the report, large volumes of chemical waste were found in downstream stretches of the Guanhe. At Helirui - a dye and chemical company - 10 metric tons of buried solid waste was dug up between August 2011 and February 2012.

Jiangsu has 953.9 kilometers of Yellow Sea coastline, most of which is near 10 coastal industrial parks that have been set up to boost the region's economy, experts said.

Situated at the mouth of the Guanhe, Guanyun county was once a thriving source of high-quality aquatic products, especially shrimp. However, because of pollution, locals who depend on farming or fishing for a living are having a tough time.

Officials of the Guanyun government said corrective measures will be promptly implemented, and they will investigate the reported illegal pipes. Intelligent management systems and real-time online monitoring will also be employed to ensure standardized sewage discharge, they said.

Jiangsu is the second-biggest contributor to China's GDP, behind Guangdong province. Wu Zhenglong, Jiangsu's governor, recently pledged to place greater emphasis on further improving air and water quality.

In a previous interview with China Daily, he said that as of the end of last year more than 1,400 chemical factories had been shut down in Jiangsu since the launch of an action plan in 2016, which was intended to cut production within high-energy consuming industries, tackle pollution and improve the ecology.

"The province is very aware that it has a long way to go to control emissions. The government will employ stricter strategies with higher standards to fight pollution and promote the economy's green transformation," the governor told China Daily during the annual session of the National People's Congress in March.