Mexico City declared a pollution emergency Tuesday because of smoke from brushfires that has cast a pall over the city of 9 million people.

The extremely small particles that are choking the city reached over 1½ times acceptable limits.

The emergency declaration is not accompanied by the usual driving restrictions because this time the pollution isn't coming from cars. The city's pollution alerts are usually triggered by high ozone levels.

The city is suspending activities that raise dust, like street sweeping and movement of construction materials.

About 45 brush and grass fires were reported in the city and its suburbs over the weekend, while dozens of fires are burning in surrounding states.