BRAZIL — Firefighters on Monday battled flames spreading through a national park in Brazil that is enveloping Brasilia in smoke. It’s the latest wildfire in the country, which is experiencing an historic drought. More than 90 firefighters were trying to extinguish blazes that have already burned through 700 hectares of the conservation area of Brasilia National Park. Two aircraft from the Federal District’s military firefighting unit and another two from the nearby Chapada dos Veadeiros national park are being mobilized, according to a statement from ICMBio, the government agency that manages the park. The head of the agency, Mauro Pires, told newspaper Folha de S.Paulo that the fire was human-caused and appears to have started near the edge of a farm. Smoke from the fire smothered the capital, Brasilia, on Monday, and columns of black smoke were visible from several points in the city.