The search for dozens of workers buried in a Tibetan landslide has continued into a fifth day on Tuesday though no survivors have been found, and experts say the rescuers are threatened by possible secondary landslides.
Rescuers had retrieved 59 bodies as of 7 p.m. Tuesday. Twenty-four others remain buried.
About 3.5 millon cubic meters of loose rocks remain on top of the mountain that served as the source of the landslide, posing a threat to the rescuers beneath, said Dorje, an academic with the Chinese Academy of Engineering.
Dorje has conducted a field investigation into the cause of the disaster, which occurred around 6 a.m. last Friday in Maizhokunggar County, about 68 km from regional capital Lhasa.
An estimated 2 million cubic meters of mud, rocks and debris struck a workers' camp of the Jiama Copper Polymetallic Mine of Tibet Huatailong Mining Development Co., Ltd., a subsidiary of the country's largest gold producer, China National Gold Group Corporation.
Dorje said loose rocks on top of the mountain triggered the landslide, indicating that the disaster was due to natural causes.
Dorje said the area from which the landslide originated was previously covered by large glaciers. Rocks hidden under the glaciers broke into smaller, loose rocks over a long period of time due to thermal expansion and contraction stress, as well as rainy and snowy weather.
He said smaller rocks near the source of the landslide collected together and snowballed into a massive landslide that was incredibly destructive.
Rescue efforts by more than 4,500 personnel have been ongoing, although they had to halt their work several times over the past two days due to fear of new landslides.
Dorje warned of the possibility of a secondary landslide, suggesting that rescue efforts should be closely monitored and include preventative measures to ensure the rescuers' safety.
Yang Zuocai, deputy commander of the rescue commanding center, said a safety mechanism had been put in place to keep the rescuers from harm.
Personnel have been stationed at every excavating site to monitor possible secondary landslides, according to Yang.
Meanwhile, an emergency passage has been set up to facilitate the retreat of rescuers in case of new landslides, he added.
Yang said the rescue efforts had not subsided, although the risks have risen as they dig deeper into the debris, which ranges from 20 meters to 50 meters in depth.
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