More than 130,000 polluting companies in the Beijing-Tianjin-Hebei region have suspended production or shut down amid comprehensive controls to curb air pollution in the autumn and winter, environmental authorities said on Tuesday.

After blue skies over the weekend, the air quality in many cities of the region including Beijing, Tianjin, and Shijiazhuang, Tangshan and Baoding in Hebei province is forecast to decline to the moderate or even severe level on Wednesday and Thursday, according to the China National Environmental Monitoring Center.

It will once again improve, reaching the good level on Friday, it added.