Inspectors from the Ministry of Environmental Protection on Sunday exposed 239 companies in the northern region with violations of illegally producing pollutants and lacking pollutant reduction equipment.

Inspectors checked 329 companies in 28 cities in the Beijing-Tianjin-Hebei region and neighboring provinces, of which 239 were found with various violations, accounting for 73 percent of those inspected, the ministry said.

Among the violations, most prominent were 69 small companies that contributed heavy pollution - when these companies should have been shut down but were still in production - and another 22 companies that had not installed equipment to reduce emissions, based on a statement from the ministry on Sunday.

The ministry sent 28 teams to 28 major cities, including Beijing and Tianjin and others in Hebei, Henan, Shandong, and Shanxi provinces, to inspect the companies, making it the ministry's largest scale inspection.

The ministry said it will conduct 25 inspection rounds from April 8 to April 8, 2018, meaning there will be a round of inspection about every two weeks.

In the first round, which is ongoing, the ministry sent 224 inspectors to these 28 cities.