KUNMING, Feb. 15 (Xinhua) -- Some 2,350 people in southwest China's Yunnan Province are working to put out a forest fire that broke out on Thursday afternoon, local authorities said Friday.

The fire erupted around 3 p.m. in the border areas between the towns of Longpan and Lashi in Yulong Naxi Autonomous County, a county government information office official said.

No casualties have been reported, but it is not yet clear how much of the forest area has been affected, the official said.

Forest police, professional fire-fighting teams, local armed forces and residents are joining the efforts to put out the fire. Helicopters are also involved in the operation, the official said.

The fire site is 100 km from the Yulong Snow Mountain, a famous scenic spot.

The cause of the fire is under investigation.