Brazilian officials say wildfires have burned about 930 square miles (2,400 square kilometers) of land inside 17 national reserves since the start of the dry season.
The government's Chico Mendes conservation institute says about 1,600 firefighters and volunteers are struggling to control the flames.
Officials say the dry season that began in June has been particularly bad this year, with less rainfall across the country and higher temperatures.
The government says the number of fires in the jungle state of Amazonas has nearly doubled this year, with more than 260 outbreaks.
Officials say the causes of the fires are often natural, such as lightning striking dry land. But they've also warned residents in the Amazon region to not light fires on their property.