In a statement Wednesday, the education ministry announced that the decree applies to both public and private schools, recommending that children should avoid rigorous activities, remain indoors and wear contact lens.
The ministry initially halted outdoor and after-school activities Tuesday.
President Andres Manuel Lopez Obrador expressed concern for the 20 million people who reside in the capital and added that the pollution was “highly regrettable,” during an addressed at a news conference Wednesday.
Tertiary institutions, the National Autonomous University of Mexico (UNAM) and the National Polytechnic Institute, also said they would be suspending classes Thursday.
Previously, on Tuesday, the Mexican government had declared an environmental emergency, which resulted from forest fires, after receiving complaints of low visibility affecting residents.
Smoke from the wildfires raised the pollution to levels that are potentially harmful to human health.
Mexico City’s Atmospheric Monitoring System (Simat) reported Tuesday that the PM2.5 index (particulate matter of 2.5 micrometers or less in diameter) had reached 160 points in some areas of the city, a number high enough to penetrate the lungs and cause serious respiratory and allergy issues.
"The environmental warning continues in the Valley of Mexico due to the prevalence of fine particulate pollution related to the presence of fires in the basin and its surroundings," the Environmental Commission of the Megalopolis (CAME) indicated.