YINCHUAN, July 23 (Xinhua) -- More than 5,200 residents have been evacuated as torrential rain battered Helan Mountain in northwest China's Ningxia Hui Autonomous Region since Sunday, local authorities said Monday.

The region saw heavy rain between Sunday night and Monday morning. The maximum rainfall during this period reached 277.6 millimeters in Helan Mountain, and floods have formed in the eastern areas at the foot of the mountain.

The regional flood control and drought relief headquarters have organized relevant departments including public security, fire, water resources and traffic to evacuate residents from affected areas.

An auxiliary police officer remains missing after being washed away by floods during the evacuation. A search operation is underway. An injured police officer is also receiving treatment at the hospital.

As heavy rainfall continues in the region and increases in the upper reaches of the Yellow River, relevant authorities have made necessary preparations for the floods.