Heavy smog has once again blanketed large parts of north and central China. It has delayed flights and prompted traffic control measures.

Heavy smog has once again blanketed large parts of north and central China.?

Nearly 20 sections of expressways have been closed as the low visibility disrupted traffic. In Hebei and Shandong provinces, the air pollution index soared to dangerous levels, prompting an alert.

In Shijiazhuang, capital of Hebei province, visibility was reduced to less than 400 meters. Weather authorities predict that as a new round of cold front blows in from northern China, the smog will be dispersed.