Extreme weather conditions killed 21 ultra-marathon runners and injured 8 on Saturday. Sudden high winds and freezing rains were witnessed by the participants of a 100 km cross country mountain race said the rescue officials.

The sudden change in weather conditions was witnessed in the Yellow River Stone Forest, which is a tourist site in Gansu province, reported Xinhua news agency.

The officials said that 21 people were killed in the tragedy out of the 172 people who participated in the run.

Most competitors were wearing thin shorts and T-shirts, according to a media report.

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Liang Jing, one of China’s well known ultra-marathon runners, was among those who died, a Hong Kong marathon group called Hong Kong 100 Ultra Marathon confirmed via a statement released on Sunday.

The marathon group said Liang had been a “favourite” member of the Hong Kong trail-racing community. He regularly participated in the annual Hong Kong 100-kilometer trail race, and was the runner-up in the last two years, it added.

It also described him as “one of the best ultra-endurance athletes in the world” and expressed condolences to his family.

The rescue work, which lasted almost 24 hours, was completed on Sunday and the remains of all 21 victims had been transferred from the site of the incident, the rescue headquarters said.

Over 1,200 well-equipped rescuers took part in the operation.

Another 151 participants were confirmed safe, of whom eight with minor injuries were treated in hospital and were in stable condition, the Xinhua report said.

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The public safety incident was caused by a sudden change in local weather. The provincial authorities have set up an investigation team to look further into the cause of the incident, Zhang Xuchen, mayor of Baiyin City told the media.

“As the organiser of the event, we feel a deep sense of guilt and remorse. We express our deep condolences and sympathies to the bereaved families and the victims,” Zhang said.

According to the rescue headquarters, at about 1 pm on Saturday, hail, freezing rain and gales hit the area of the race’s high-altitude stage, between 20 km and 31 km. Participants suffered from physical discomfort due to the sudden drop in air temperature.

The race was halted when some participants went missing.

“At 1 pm on Saturday, the wind got stronger. It was hard to stand up straight and move forward. When the wind was the strongest, I had to grasp the ground with both my hands to avoid being blown over,” Xinhua quoted one survivor, who declined to be named, as saying.

“I felt nothing but cold at the time,” said the survivor.

“I just ran about 30 km and quit the race ahead of the third checkpoint. I fainted halfway down the mountain.” After participants posted videos requesting help in a WeChat group chat, local authorities initiated an emergency response and organised rescue forces to search for the missing people.

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The temperature dropped again during the night due to the area’s complex terrain and topography, making the search and rescue work more difficult, according to the rescue headquarters.

The tragedy has evoked public anger on Chinese social media, with criticism mainly directed at the Baiyin government for lack of contingency planning.