About 2,000 firefighters have been sent to put out a forest fire that broke out on Tuesday afternoon in north China's Inner Mongolia Autonomous Region.

As of 5 p.m. Wednesday, fire was still raging in the primitive forest in the Hanma National Nature Reserve in Inner Mongolia, said the regional forest fire prevention headquarters.

The windy weather in the forest is making it extremely difficult to extinguish the blaze, added the headquarters.

As of 6 p.m. Wednesday, the fire has extended to an area of about two square kilometers, with local authorities ready to undertake artificial precipitation in accordance with the weather conditions to slow its spread.

According to preliminary investigation, the forest fire was caused by a thunder strike. The exact cause is still under investigation, however.