A curtain of smoke from wildfires in the Amazon rainforest is spreading across Brazil, making its way to Sao Paulo and possibly heading toward neighboring countries Argentina and Paraguay.

There were 28,697 fires reported in the Amazon region in August, 38% higher than the 10-year average, WWF-Brasil said, citing data from the National Institute for Space Research known as Inpe. The number exceeds 50,000 in the year to Aug. 27, the most since 2010, it said.

Toxic particles smothered the capital Brasilia in recent days and now have spread to Sao Paulo, the country’s financial center and Latin America’s biggest city. Blazes have been reported in the Pantanal wetlands and throughout the countryside of Sao Paulo state, while fire in the nation’s sugar-cane fields, the world’s top exporter, is set to impact the global supply of sweetener.