More than 2,500 people have been sent to extinguish a forest fire raging in southwest China's Yunnan Province, local authorities said on Monday. The fire, which broke out at noon on Saturday on Ninan Mountain in Baoshan City, has so far engulfed about 1,200 mu (80 hectares) of forest, according to publicity officials with the city's Longyang District. Two helicopters were sent to help firefighters including armed police and soldiers put out the fire, but the efforts were hampered by gales, the lushness of the forest and complicated terrain, officials said. No casualties have been reported so far, and the cause of the fire is yet to be determined. Forest fires are common in Yunnan, over half of which is covered with forest. At least three such fires have been reported since the beginning of this month.