Police officers of the Hohhot railway public security section are on patrol along the Zhangjiakou-Hohhot high-speed railway in Ulanqab of north China's Inner Mongolia Autonomous Region, Feb. 3, 2021. (Xinhua/Lian Zhen)

Police officers of the Hohhot railway public security section are on patrol along the Zhangjiakou-Hohhot high-speed railway in Ulanqab of north China's Inner Mongolia Autonomous Region, Feb. 3, 2021. (Xinhua/Bei He)

Aerial photo taken on Feb. 3, 2021 shows police officers of the Hohhot railway public security section on patrol along the Zhangjiakou-Hohhot high-speed railway in Ulanqab of north China's Inner Mongolia Autonomous Region. (Xinhua/Lian Zhen)

Police officers of the Hohhot railway public security section are on patrol along the Zhangjiakou-Hohhot high-speed railway in Ulanqab of north China's Inner Mongolia Autonomous Region, Feb. 3, 2021. (Xinhua/Bei He)

Police officers of the Hohhot railway public security section are on patrol along the Zhangjiakou-Hohhot high-speed railway in Ulanqab of north China's Inner Mongolia Autonomous Region, Feb. 3, 2021. (Xinhua/Bei He)