Around noon on Saturday, a mountainous section of the race was hit by hail, freezing rain and gales, with temperatures falling sharply, officials from Baiyin told a news briefing on Sunday. The route would take runners through deep canyons and undulating hills on an arid plateau at an elevation of more than 1,000 metres (3,300 feet).
Other 151 mountain marathon participants were confirmed safe, of which eight with minor injuries were treated in the hospital.
However, Baiyin city's local branch of the National Early Warning Information Center had warned for the past three days of hail and strong winds.
Some went missing in the extreme weather on Saturday afternoon, when the 100-kilometre race in the Yellow River Stone Forest tourist site in Baiyin city in Gansu province was halted.
The runner opted to quit the race.
Some Chinese media reports say the local government that organized the event did not warn the runners of the risk of cold weather because a daytime high of 19 degrees Celsius had been forecast.
The most hard section is from mile 15 to mile 22, where it climbs 3,820 feet. The path there is a mix of stones and sand, a runner told the Paper via AP. During the race, he said, the wind picked up and it started to rain. He made it back to safety amid rapidly dropping temperatures.
Photos published by Chinese media also showed a group of runners huddled together on the mountainside, some wrapped in insulation blankets. Numerous runners suffered from hypothermia.
But the weather caught them off guard, and on the morning of the race Saturday, he already sensed things were not normal.
The marathon organizers called off the race and launched a search party of 1,200 people to scour the complicated terrain. "I fainted halfway down the mountain".
Long-distance running has gained popularity in China in recent years with the country's growing middle class taking up the sport.
"He was a "favorite" member, they said", and "one of the best ultra-endurance athletes in the world".
Baiyin City Mayor Zhang Xuchen said Sunday that provincial authorities will further investigate the incident, but Chinese social media exploded with outrage directed at the local government for not planning more carefully, the Guardian reported.