Another 28,600 firms were ordered to suspend their operations, the Ministry of Environmental Protection said today.

Among the violators, 46,800 enterprises were found to have discharged pollutants and 63,700 were involved in illegal construction projects, the ministry said.

The ministry received has 73 public tip-offs about pollution lodged through the 12369 telephone hotline in September.

The industries most complained about were chemicals, metal smelting and processing and non-metallic mineral processing.

In November, the ministry dispatched inspection teams to 504 enterprises across the country, including Beijing, Tianjin, Hebei, Inner Mongolia, Guangdong and Xinjiang.

During the inspection, violations were found in urban treatment of dust, central heating and oil vapor recovery in petrol stations, the ministry said.