BEIJING, Jan. 15 (Xinhua) -- Although Beijing's smoggy air began to clear late Monday due to a light snowfall, the city's air pollution remains at high levels.
The snow, which lasted until 7 a.m. Tuesday, reduced the concentration of fine particulate matter in the air to 50 to 70 micrograms per cubic meter, according to the data released by the city's environmental monitor center.
The city's weather bureau lifted its fog alert at 6 a.m., with visibility in most areas increasing to more than 10 km by 3 p.m., the bureau said.
Air quality indices reached the "medium to dangerous level" Tuesday morning. The indices were literally off the charts during the preceding five days, exceeding the "maximum" level of 500.
The weather bureau said wind will sweep the city from Tuesday evening to Wednesday. Air quality is expected to improve after the wind disperses the smog.
Lingering clouds of smog have been spotted in many parts of China in recent days, affecting traffic and sending some people to the hospital for respiratory ailments.
Four deaths have been attributed to the smoggy weather, including two high school students who were hit by a train due to low visibility in the city of Chaohu in east China's Anhui province on Monday.
Another two were killed in a pileup involving 20 vehicles in neighboring Zhejiang province early Tuesday morning. Eight others were injured.
The low visibility also prevented authorities from spotting a furniture factory fire in Zhejiang, with the fire raging for four hours late Monday until neighbors spotted the fire and called firefighters. No casualties have been reported in connection with the fire.
Residents in many cities have been advised to stay indoors. Regular outdoor activities, such as morning exercise activities and flag-raising ceremonies, have been held indoors.
Government authorities have launched traffic control measures and suspended factory production in order to curb the pollution.
In the city of Jinan in east China's Shandong province, the local government on Tuesday cut the number of both government and private vehicles on the road in half according to their license plate numbers, allowing even-numbered license plate owners to drive on some days and odd-number drivers to drive on others. The measure is in effect until further notice.
Experts have urged local governments to exert concerted efforts to reduce the smog.
Ma Jun, director of Beijing's public environment research center, said factories in neighboring cities have affected the city's air quality.
Factories can be seen in large numbers in the cities of Tangshan, Shijiazhuang and Handan, all of which are located south of Beijing in Hebei province.
"On Saturday morning, the sky was still blue in some parts of Beijing, but it became smoggy by noon because of wind bringing polluted air from the south," Ma said.
Ma advised municipalities, provinces and autonomous regions in north China, including Beijing, Tianjin, Hebei, Shanxi, Henan, Shandong, Inner Mongolia and Liaoning, to work together to come up with a joint method to reduce pollution.