The ultramarathon in the Yellow River Stone Forest, near Baiyin city in Gansu province, on Saturday left a further eight of the 151 runners injured, officials said.
According to the city’s mayor, temperatures suddenly plunged with strong winds bringing hailstones and icy rain as runners entered the mountainous section.
Competitors involved in the race have been sharing their first-person accounts of the conditions as organizers face a backlash on Chinese social media for a perceived lack of contingency planning.
Messages between participants on a private WeChat group reported that some runners had suffered from hypothermia after losing their way.
“The wind is too strong, our thermal blankets have been torn to bits,” one runner wrote, according to a Reuters report.
“A few are unconscious and are foaming at the mouth,” another said.
Screenshots of the messages were shared with the news agency by runner Mao Shuzhi, who pulled out of the race about 24 km in before the high-altitude section.
“The rain was getting heavier and heavier,” Shuzhi said.
Participants were racing on an extremely narrow mountain path at an altitude reaching 2,000-3,000 meters (6,500-9,800 feet), the Associated Press reports.
A reporter for state broadcaster CCTV said some runners fell off the trail into deep mountain crevices.
Another runner wrote about his experience on his WeChat account “Wandering about the South” in an account that has been viewed more than 100,000 times.
“I ran 2 kilometers before the starting gun fired to warm up … but the troublesome thing was, after running these 2 kilometers, my body still had not heated up.”
He said he decided to turn back when he began to feel dazed and was later met by members of the huge rescue crew, AP reported.
The horrendous weather conditions struck around noon local time—about three hours into the race—as runners began the high-altitude section of the race between 20-31km.
“In a short period of time, hailstones and ice rain suddenly fell in the local area, and there were strong winds. The temperature sharply dropped,” Baiyin city mayor, Zhang Xuchen, told reporters at a press briefing on Sunday.
A major search and rescue operation involved more than 700 rescuers and soldiers used thermal-imaging drones and radar detectors.
Temperatures dropped further overnight on Saturday, according to the Xinhua news agency, hampering the search.
The disaster has sparked public outrage in China, with many commentators reportedly questioning the organizers’ preparations on social media.
Xuchen told reporters on Sunday: “As the organizer of the event, we are full of guilt and remorse. We express deep condolences and sympathy to the families of the victims and the injured.”
