Baiyin Mayor Zhang Xuchen said at a press briefing that the mountain competition began on Saturday morning in a tourist area in the Yellow River Stone Forest, with the participation of 172 people.
However, shortly after noon, a gust of hail, freezing rain and gales suddenly struck a 20-30 kilometer high-altitude section of the race.
The marathon was suspended because the runners suffered physical discomfort and loss of body heat due to low temperatures, while some went missing, the official said.
Thousands of rescuers have explored the area since Saturday, but found the last missing runner at dawn.
According to the official report, 151 individuals are safe, eight suffered from minor injuries and one is seriously ill but remains stable.
The local Government opened an investigation into the tragedy, as the mountain marathon covered a 100-kilometer route and some parts of the area register temperatures close to zero degrees Celcius.