Eighteen people have been detained after central inspectors uncover 2,500 pollution cases, the Ministry of Environmental Protection said on Wednesday.

As of Monday, inspectors had received more than 4,300 calls and letters about suspected pollution in seven provincial-level regions.

The Ministry of Environmental Protection said 2,563 cases of pollution in the regions targeted have now been confirmed.

Of the confirmed cases, the provincial governments have dealt with 497 cases ordering 559 companies to stop pollution and improve their equipment.

As a result of the investigation, 18 people found responsible for the pollution have been detained, and 275 officials have been held accountable, the Ministry said.

Seven inspection teams, headed by ministerial level officials, started a month-long environmental inspection last week, covering Beijing, Shanghai and Chongqing, and the provinces of Hubei, Guangdong, Shaanxi and Gansu.

Since Sunday, the inspection team in Chongqing has started a field investigation, a major step in the process, and other teams will follow soon, the Ministry stated.

The inspection teams will also review the governments' performance at the provincial and local levels to see if they have met set standards or neglected their duties in relation to pollution control, and will investigate major issues frequently reported by the public.