Wildfires spread across Brazil's most populous state of Sao Paulo Friday, prompting highest-level alerts in 30 cities and filling the capital's skies with smoke.

Low humidity and temperatures topping 35 degrees Celsius (95 degrees Fahrenheit) were exacerbating fire conditions in the southeast region, which is facing a prolonged drought.

The Sao Paulo state government set up a crisis cabinet Friday night to coordinate work on battling the flames.

"We currently have 30 cities on high alert for large fires and we are working to control the situation and ensure safety," Governor Tarcisio de Freitas said on X.

Local authorities said two workers died at a factory in the municipality of Urupes, in the north of the state, while trying to fight a fire.

The flames also generated significant transport disruptions, with low visibility due to smoke bringing traffic to a total or partial standstill on a dozen highways.

Meanwhile, the state's eponymous capital Sao Paulo was covered by a dense gray fog.

"With gusts of wind, the fire can spread rapidly," the government warned in a statement.

"Fires emit dense and toxic smoke that harms the environment and human health, causing problems to the respiratory system and cardiovascular disorders," it added.

The situation was critical in Sao Jose do Rio Preto, a city of 480,000 inhabitants, where more than 335 fires have been registered in recent days, prompting school closures.

Brazil has been battered by a series of extreme weather events, most recently a massive wildfire in the Pantanal wetlands and once-in-a-century flooding in the state of Rio Grande do Sul that left more than 170 people dead.