Heavy pollution, smog shroud northern areas

Capital raises four-tier health alert, while some expressways closed due to limited visibility

Residents in vast northern and northeastern regions awoke to encounter severe smog on Friday, prompting Beijing to raised its health alert.

Visibility dropped to below 200 meters in some areas, including the capital and the southern region of Liaoning province on Friday morning due to pollution mixed with heavy fog, leaving some expressway sections closed for hours.