Smoke from wildfires has brought life in Brazil's biggest Amazon city to a halt.

The city of Manaus, capital of Amazonas state, canceled public school classes and suspended in-person work at city offices on Friday because of poor air quality, the Associated Press reported via Newsday. Residents were urged to wear face masks.

The city said pollutant levels averaged 196 micrograms per cubic meter. That is an unhealthy level, far above the normal range of about 3 to 9.

On Oct. 10, Amazonas state declared a state of emergency in 36 municipalities because of forest fires and heavy smoke, UA.News reported. The federal government recognized the decree the same day. That lets authorities request federal money and send aircraft to fight fires.

The emergency covers Manaus and its metro area, the southern part of the state and several river cities, including Itacoatiara, Parintins, Tefé, Humaitá and Lábrea.

Brazil's dry season is nearing its peak. Many fires in the Amazon are set on purpose to clear land for farming and cattle, then spread out of control in dry conditions. Drought, made worse by climate change and weather patterns like El Niño, helps fires grow.

Smoke from fires can cause breathing problems, especially for children, older people and those with asthma or heart disease. Doctors advise staying indoors with windows closed when air quality is bad.

The Amazon is the world's largest rainforest. It stores huge amounts of carbon, and scientists warn that repeated fires and drought could push parts of it to turn into dry savanna.

What we know: Amazonas has declared an emergency, and smoke has closed schools in Manaus.
What we don't: when federal aircraft will arrive or when the air will clear.