BEIJING (AP) — Engulfed in choking smog, some northern Chinese cities limited the number of cars on roads and temporarily shut down factories Monday to reduce air pollution during a national “red alert.”

More than 700 companies stopped production in Beijing and traffic police were restricting drivers by monitoring their license plate numbers, state media reported. At least 23 cities in the world’s most populous country have issued red alerts for air pollution since Friday, according to the official Xinhua news agency. Authorities in the northern province of Hebei, which surrounds Beijing, ordered coal and cement plants to temporarily shut down or reduce production. Adding to a sense of crisis, local news in recent days reported that hospitals were encountering a boom in cases of children with respiratory problems and preparing teams of doctors to handle the surge of pollution-related cases. BEIJING (AP) — Thick, gray smog fell over Beijing on Tuesday, choking China’s capital in a haze that spurred authorities to cancel flights and close some highways in emergency measures to cut down on air pollution. In nearby Tianjin, authorities canceled 350 flights and closed all highways in the municipality.
Companies shut down production in Beijing and cars are taken off the road after a red alert for smog is issued in northern China. Dozens of cities have closed schools due to the smog.