Firefighters worked to extinguish flames Wednesday engulfing forest and pastures of the Los Santos Forest Reserve near San Marco de Terrazú, south of San José.
The fire started Tuesday and by Wednesday morning had burned through some 35 hectares. Officials were ready to issue an alert for the canton of Santa María de Dota should the fire spread, the Environment Ministry said.
The hilly terrain and high winds made it difficult to contain the blaze despite efforts by area residents, volunteers and National Forest Fire Commission workers, the ministry said in a press release Wednesday.
National Police were set to fly over the area Wednesday afternoon to assess the damage and begin to investigate what caused the fire.