Mexico City closes schools, restricts traffic due to smoke

A man wearing a face mask crosses a street backdropped by the National Palace shrouded by haze, in the Zocalo, Mexico City's main square, Thursday, Ma

A man wearing a face mask crosses a street backdropped by the National Palace shrouded by haze, in the Zocalo, Mexico City's main square, Thursday, Ma

Cuban tourist Fernando Castillo wears a face mask as he sits on a bench on pedestrian Madero Street in the historic center of Mexico City, Thursday, M

Cuban tourist Fernando Castillo wears a face mask as he sits on a bench on pedestrian Madero Street in the historic center of Mexico City, Thursday, M

A man wearing a face mask crosses a street by the Metropolitan Cathedral, shrouded by haze, in the Zocalo, Mexico City's main square, Thursday, May 16

A man wearing a face mask crosses a street by the Metropolitan Cathedral, shrouded by haze, in the Zocalo, Mexico City's main square, Thursday, May 16

Maria Del Carmen Pineda Gomez, who says she is suffering from a respiratory infection that began three days earlier, wears a mask to protect herself a

Maria Del Carmen Pineda Gomez, who says she is suffering from a respiratory infection that began three days earlier, wears a mask to protect herself a

A woman covers her nose and mouth with a scarf as she walks on pedestrian Madero Street in the historic center of Mexico City, Thursday, May 16, 2019.

A woman covers her nose and mouth with a scarf as she walks on pedestrian Madero Street in the historic center of Mexico City, Thursday, May 16, 2019.

MEXICO CITY (AP) — Mexico City officials have cancelled classes for millions of students as smoke from brush fires continues to choke the city of 9 million.

A light rain overnight has done little to cut the pollution, which remained at about 1 ½ times acceptable limits.

The city declared a partial driving ban, but activists of the Citizen Observatory on Air Quality called Thursday for officials to limit polluting activities like trucks and construction sites.

The activists said the city should include extremely small particles as a cause for imposing emergency measures. Such particles are frequently found in smoke, diesel exhaust and dust. Emergency measures are currently imposed mainly for ozone levels.

The group said "forest fires are unfortunately going to be an ever more frequent problem as a result of global warming."