Air pollution in Beijing has reached hazardous levels as smog engulfed large parts of the country despite efforts to clean up the foul air.

The U.S. Embassy in Beijing reported the level of the poisonous, tiny articles of PM2.5 at 391 micrograms per cubic meter at noon Saturday. The World Health Organization considers the safe level at 25 micrograms per cubic meter of the particulates.

The Ministry of Environmental Protection has forecast severe pollution for the greater Beijing region, as well as the west part of Shandong and the northern part of Henan until Tuesday, when strong winds from the north are expected to blow away air pollutants.

The ministry has advised the public to stay indoors.