More than 1,000 fire fighters, forest police officers and soldiers are battling a fire that has engulfed 400 mu (26.7 hectares) of forest in southwest China's Yunnan Province as of Tuesday night, said local forest fire control authorities.

The fire broke out at about 11:00 a.m. Tuesday in a forest in Baoshan City and continued to spread due to strong winds, said a spokesman with the headquarters.

No casualties have been reported, said the spokesman.

Strong winds and the complex forest terrain hindered efforts to put out the fire. However, the fire is expected to be put out before dawn on Wednesday since the wind drops after midnight, he said.

The headquarters also dispatched a helicopter from Dali, about 180 kilometers northeast of Baoshan, to fight the fire.

An investigation into the cause of the fire is underway.