0458 GMT May 24, 2019
Air quality index (AQI) readings at some monitoring stations in Tianjin, a port and industrial city southeast of Beijing, peaked above 400, Xinhua said. Anything above 300 is considered hazardous by the U.S. Environmental Protection Agency.
China's environmental watchdog issued a five-day warning on Friday about choking smog spreading across the northeast and ordered factories to shut, recommended residents to stay indoors and curbed traffic and construction work.
Pollution alerts have become increasingly common in China's northern industrial heartland, especially during winter when energy demand – much of it met by coal – skyrockets.
In addition, heavy winds force pollution from nearby provinces to the Beijing-Tianjin area where it remains suspended over the cities.
By 10 a.m. on Sunday in Tianjin, 35 international flights had been delayed or canceled and all highways in and out of the city, with one exception, were shut.
With the density of pollutants expected to peak on Sunday and Monday, Tianjin's Environmental Protection Department had strengthened inspections to control sources of pollution including factories.
Tianjin was placed on orange alert – the second highest level – on Sunday. On Saturday, 22 cities issued red alerts including top steelmaking city Tangshan in Hebei Province around Beijing, and Jinan in coal-rich Shandong Province.
Red alerts are issued when the AQI is forecast to exceed 200 for more than four days in succession, 300 for more than two days or 500 for at least 24 hours.