BRASILIA, Brazil -- The buildings in Brazil's modernist capital, Brasilia, have been enveloped in smoky air the past two days. The central part of the country is just the latest region affected by smoke from fires in the Amazon rainforest, Cerrado savannah, the Pantanal wetland and the state of Sao Paulo.

The smog crisis prompted President Luiz Inácio Lula da Silva to visit Brazil's fire monitoring center Sunday afternoon. “No fires caused by lightning were detected. This means that people are intentionally setting fires in the Amazon, the Pantanal, and especially in the state of Sao Paulo,” he said. His government vowed to intensify firefighting efforts and investigations to identify those responsible.

Fire alerts so far this month total almost 3,500 in southeastern Sao Paulo state — the highest number recorded in any month since data collection began in 1998. Over half those fires occurred on Aug. 23, raising suspicions of a coordinated attack. The smog caused 48 cities to declare a red alert. The good news was that a cold front Monday brought declining temperatures and rain, extinguishing all fires, the state government said.

Brasilia's air quality index reached a dangerously unhealthy level on Sunday evening, according to the city's environmental agency. This marked the first time the agency had issued a smog alert since its establishment in 2007. Public events were canceled, and the airport in the nearby city of Goiania was temporarily closed.

Amazon cities such as Manaus, Porto Velho and Rio Branco have been grappling with smoke for several weeks but have received less official and media attention. This is partly because it´s an annual occurrence.

“It took the smoke and soot from the Amazon and the Cerrado invading the halls of the presidential palace for the federal government to take action,” Altino Machado, a journalist based in Rio Branco who has been writing about the environment for four decades, told The Associated Press.

In the state of Sao Paulo, two workers at an industrial facility lost their lives on Friday while attempting to control a blaze. Moreover, an association representing sugarcane producers reported the destruction of 59,000 hectares (146,000 acres) of sugarcane plantations. In the Amazon, a federal firefighter also died on Monday while working in the Capoto Jarina Indigenous Territory.

According to Karla Longo, a researcher who tracks smoke at the National Institute for Space Research, a federal agency, the haze that shrouded Sao Paulo state and Brasilia originated partly from the Amazon, Pantanal, and Cerrado regions. Longo attributed the smoke's arrival to shifts in weather patterns.

During the driest months of August and September, when wildfires and deforestation reach their peak, the smog typically extends up to 5 million square kilometers (1.9 million square miles), moving from east to west and then south after encountering the Andean Cordillera. Earlier this month, it reached Rio Grande do Sul, Brazil's southernmost state.

However, Longo explained that a cold front shifted the smog towards Sao Paulo state, which was already experiencing an unprecedented number of fires, and then spread to Brasilia's region.

The researcher also noted that the number of wildfires in Brazil this year is not unusual. However, she highlighted that the areas affected by fire are larger than average. From January to July, an area the size of Italy had been burned — 64% more than the same period last year, according to official data. Fires are traditionally used as a final step in deforestation and for pasture management.

Almost half of Brazil's carbon emissions are attributed to deforestation. The country ranks fifth globally in greenhouse gas emissions, accounting for nearly 3% of global emissions, according to Climate Watch, an online platform managed by the World Resources Institute.

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AP reporter David Biller, based in Rio de Janeiro, contributed to this article.

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