The four geological surveyors who mysteriously went missing in the Ailao Mountains, southwest China's Yunnan Province, last month died from cardiogenic shock induced by low temperature, according to a report released on Wednesday.

The missing of these reportedly experienced geologists and eventual death after a massive search and rescue mission have caught people's attention, who wondered why the ex-servicemen reportedly well-equipped with food and positioning devices could have all died without apparent injuries. Many speculated that it might have been a case of animal attacks, poisonous fog or extreme weather.

A medicolegal examination excludes poisoning and mechanical injury from the possible causes of death, according to the China Geological Survey, which the four victims worked for. The department is affiliated with the Ministry of Natural Resources.

A panel of specialists concluded following an on-site investigation that the four suffered physical exhaustion from prolonged mountain-climbing before they were finally knocked down by body temperature loss, which was caused by instantaneous gales and sudden temperature plunge.

Zhang Jinbang, Yang Min, Liu Yu and Zhang Yu had entered the Ailao Mountains area for forestry resources survey from Zhenyuan County of Pu'er City on November 13. They were reported missing two days later.

A sweeping search mission was soon launched, which involved several thousand rescuers and dozens of helicopters and drones. Three of them were found dead on November 21. The next morning, the body of the remaining member was found several hundred meters away.

Their bodies were transported out of the mountain on November 24 following a 38-hour operation, according to the command center of the rescue mission set up by the local government.

Situated in central Yunnan, the Ailao Mountains are the boundary between the Yunnan-Guizhou Plateau and the Hengduan Mountains. A large part of the range is classified as the national-level nature reserve due to its abundant natural resources. The area is known for its high and precipitous terrain.

According to a report by The Paper, the surveyors, aged between 25 and 32, were well equipped for this field operation. They brought along various things, including a real-time kinematic (RTK) instrument, laptop, forestry compass, shovel, knife, bear spray, and some food.

Their bags still had food remaining when they were found. The report also quoted a local official as saying that their satellite phone was left in the car and was not with them.

The China Geological Survey said the crew received training ahead of the mission. They had finished surveying more than 30 sample plots before this mission.

Sadly, this is not the only case in which people were killed by extreme weather in the country this year. Twenty-one runners died after hail, freezing rain and high winds hit them during a 100-kilometre cross-country mountain marathon race in northwest China's Gansu Province on May 23.

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