Some of the participants went missing and the race was halted.
They "described to us people foaming at their mouths, and urged us to quit the race as soon as possible", she said.
'While descending the mountain, I was already experiencing hypothermia symptoms'. Hundreds of rescue personnel who reportedly took part in search operations found their efforts were impeded at times by the rugged terrain, a landslide and falling temperatures overnight.
Participants suffered from loss of temperature due to the sudden drop in air temperature.
Gansu Meteorological Bureau warned of "sudden heavy showers, hail, lightning, sudden gale-force winds" and other adverse weather conditions across the province in a report dated Friday.
Temperatures dropped suddenly Saturday as hail, freezing rain and strong winds inundated the mountain, the Associated Press reported.
According to the Chinese website cnnb.com as well as Hong Kong running store Gone Running, elite Chinese runner Jing Liang, who had won all three previous editions of this race, was among those who died.
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But the weather caught them off guard, and on the morning of the race Saturday, he already sensed things were not normal.
"At first I was a bit regretful, thinking it might have just been a passing shower, but when I saw the strong winds and rains later through my hotel room window, I felt so lucky that I made the decision", Mao told Reuters.
But the one thing he excelled at was running - so he joined races over the years in the hopes of winning some prize money, his friends were quoted as saying.
Temperatures dropped again during the night due to the area's complex terrain and topography, making the search and rescue more hard, Xinhua said.
Chinese social media erupted in mourning and outrage on Sunday, as users blamed organisers for perceived failings in contingency planning.
Marathons and extreme sports have seen a surge in popularity among China's middle class in recent years.
However, Chinese marathons have often been plagued by cheating scandals. Numerous runners suffered from hypothermia.