BEIJING - The Ministry of Environmental Protection on Wednesday reported malpractice in Hebei, the province that produces most of China's steel, after sending inspection teams to smog-hit regions.

It was found that some thermal power plants, cement and steel makers failed to halt or curtail production during severely smoggy days, said the ministry in a statement.

Small coal burning boilers in main urban areas were not shut down as required. Other malpractice included ineffective controls against dust pollution in construction sites.

According to the ministry, 12 inspection teams were sent to Beijing, Tianjin, Hebei Province and their surrounding areas on Sunday, to review the local governments' response to air pollution.

Violations revealed by the inspection teams will be harshly punished, vowed the ministry.

Almost all provinces in central and east China have been under a cloud since Friday, while Beijing and the provinces of Hebei, Shanxi, Shandong, Henan and Liaoning have reported "severe smog."

A strong cold front is expected to arrive on Thursday and disperse the smog.