Rescuers said Sunday that at least 20 people were killed in a mountain marathon cross-country race in northwestern China after hail, freezing rain, and gale winds struck the high-altitude course.

Participants suffered from physical pain and a sudden drop in temperature, according to the rescue headquarters, which was cited by the official Xinhua News Agency.

When the 100-kilometer race in the Yellow River Stone Forest tourist site in Baiyin City, Gansu province, was halted at 1 pm on Saturday due to severe weather, some people went missing.

According to state broadcaster CCTV, 20 people were found dead early Sunday and one was missing. The operation, which was complicated by low nighttime temperatures and the area's complex terrain and topography, involved over 700 rescuers.

A total of 172 people participated in the race, with 151 reported safe and one runner still missing. Officials said eight runners were treated for minor injuries and were in good health.

Due to the area's complicated terrain and topography, temperatures fell again during the night, making search and rescue more difficult, according to Xinhua.

The rescue effort was also delayed by a landslide caused by the extreme weather, according to Baiyin officials.