At least 20 people have died and one person is missing after hail, freezing rain and high winds hit runners taking part in a 100km (62-mile) cross-country mountain race in China.

More than 700 rescuers and army personnel were deployed to find runners caught by the storm in the race in Yellow River stone forest near Baiyin in north-western Gansu province, officials said.

Twenty people died, eight were injured and one remained missing at 8am on Sunday morning Beijing time, officials from Baiyin told a news briefing.

“According to the rescue headquarters, at about 1pm Saturday, hail, freezing rain and gales hit the area of the race’s high-altitude stage between 20-31km,” the Xinhua news agency reported.

“Participants suffered from physical discomfort and loss of temperature due to the sudden drop in air temperature. Some of the participants went missing and the race was halted,” it said.

Temperatures in the mountainous terrain dropped further overnight, Xinhua said, making search and rescue “more difficult”.

“As of 3am Sunday, 151 participants have been confirmed to be safe, of which five with minor injuries are being treated in the hospital and in stable condition,” it said.

Gansu, one of China’s poorest regions, borders Mongolia to the north and Xinjiang to the west.

Deadly floods and landslides have hit the province in the past, with mudslides reportedly killing well over 1,000 people in one town in 2010.

It is also prone to earthquakes.

Yellow River Stone Forest is famous for its rugged mountain scenery marked by stone stalagmites and pillars, and is used as a location in many Chinese television shows and movies, according to the China Daily.

Its rock formations are believed to be 4 billion years old. Xinhua said a total of 172 people were taking part in the race.