Twenty-one people were killed when extremely cold weather struck during an ultramarathon on Saturday in China's northwestern Gansu province, state media reported on Sunday.
The 100-km (62-mile) race began in a lush tourist site at a bend in the Yellow River, China's second-longest. The route would take runners through deep canyons in a rugged landscape.
The race kicked off on Saturday morning with runners clad in t-shirts and shorts under overcast skies, according to photographs posted on the social media account of the Yellow River Stone Forest scenic area in Jingtai, a county under the jurisdiction of Baiyin city.
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.
A total of 172 people took part in the race. By Sunday, 151 participants had been confirmed safe, including the injured, the official Xinhua news agency reported.
Eight were lightly injured as of 8 a.m. Beijing time (0000 GMT) on Sunday, the Baiyin officials said.
A massive rescue effort has been initiated, with over 1,200 rescuers dispatched, assisted by thermal-imaging drones, radar detectors and demolition equipment, according to Xinhua.
Temperatures dropped again during the night due to the area's complex terrain and topography, making the search and rescue more difficult, Xinhua said.
The last missing runner was found dead at 9:30 a.m. on Sunday, state television reported.
A landslide following the severe weather also hampered the rescue work, said officials from Baiyin, about 1,000 km west of the Chinese capital Beijing.