The cities have been affected by dry, hot weather in recent days, the government said in a statement, Reuters reported.
The state government also warned that forest fires could spread rapidly from gusts of wind, potentially razing large areas of natural vegetation.
For now, the government has not reported flames directly reaching the city of Sao Paulo, Latin America’s largest by population with more than 11 million residents.
Still, local media reported smoke blocking out some parts of state capital’s sky.
The government said two employees at an industrial plant in the city of Urupes had died on Aug 23 while fighting a fire, without providing more details.
Earlier in the day Raizen, the world's largest sugarcane processor, said that industrial operations at a plant in Sertaozinho had been halted since Aug 22 due to fires in sugarcane fields around the plant.
The Sao Paulo state government has created an emergency committee to handle the fires, which had also blocked some 15 highways either fully or partially.
Brazil's wildfire season typically peaks in August and September.
This year wildfires started unusually early in Pantanal, the world's largest wetlands, in late May, while the number of fires in the Amazon rainforest surged to a two-decade high for the month of July, government data showed early this month.