Hong Kong , China ( CNN ) -- Air pollution at or near record levels in Hong Kong on Monday was caused by a sandstorm from northern China , environmental officials said . The Environmental Protection Department urged people , especially those with breathing or heart problems , to stay indoors and limit physical exertion . Schools had been ordered to cancel sports activities , said Environment Secretary Edward Yau , according to Radio Television Hong Kong , a public television station . Hong Kong 's air pollution has grown progressively worse during the past two decades , as pollution from mainland China has blended with pollution generated by Hong Kong . Watch video of sandstorm blanketing Beijing . Over the years , poor air quality has even affected the view across Victoria Harbor , which separates Hong Kong Island from the Kowloon Peninsula by less than 1 kilometer ( 0.6 mile ) at the narrowest point . On days with heavy pollution , the vibrant lights and skyscrapers on either side of the harbor can not be seen from the other side .
Air pollution reaches near-record levels , Hong Kong government says . Officials : Sandstorm in mainland China causing the pollution .