“Abrupt, extreme weather” hit a high-altitude section of the 100-kilometre cross-country race held in the Yellow River Stone Forest near Baiyin city at around noon (04:00 GMT) on Saturday, officials said during a briefing on Sunday.
Shortly after receiving messages of help from some participants, marathon organisers dispatched a rescue team that managed to save 18 participants, he said.
At about 2pm (06:00 GMT), weather conditions worsened and the race was immediately called off as local authorities sent more rescuers to help, Zhang added.
“This incident is a public safety incident caused by sudden changes in weather in a local area,” he said, adding that provincial authorities will further investigate its cause.
A further eight runners were being treated in hospital for minor injuries, Zhang said.
A total of 172 people took part in the race. As of Sunday, 151 participants had been confirmed safe, including the injured, the official Xinhua news agency reported.
Temperatures in the mountainous terrain dropped further overnight, Xinhua said, making search and rescue “more difficult”.
A landslide following the severe weather also hampered the rescue work, the Baiyin officials 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 more than 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 four billion years old, the Daily said.
SOURCE: NEWS AGENCIES