China's Ministry of Environmental Protection (MEP) said Sunday that air quality inspection teams found problems in 21 companies and construction sites in the previous two days.
The teams were sent to check more than 2,100 monitoring spots in 28 cities in the Beijing-Tianjin-Hebei region and neighboring areas, including Shanxi, Shandong and Henan provinces, according to MEP.
On Friday and Saturday, six companies in Hebei Province, four in Shanxi and one in Henan failed to implement requirements to suspend or limit production under orange alerts for heavy air pollution.
China has a four-tier color-coded warning system for severe weather, with red being the most serious, followed by orange, yellow and blue.
Eight construction sites failed to stop the work and two companies were found to have emission levels higher than allowed.
China has defined pollution control as one of the "three tough battles" for the next three years, according to the central economic work conference.