Six people had been pulled alive from the mine in Inner Mongolia by 10.30pm (1430 GMT) on Thursday, state media reported on Friday.
The open-pit mine operated by small local firm Xinjing Coal Mining Co collapsed in a landslide on Wednesday, leaving workers buried under a pile of debris about 500 metres wide and an estimated 80m high, state broadcaster CCTV said.
A second landslide halted rescue efforts, state media reported, with the risk of more collapses very high.
An avalanche of rock and soil could be seen in CCTV footage falling from one side of the mountain into the mine pit, burying a number of excavators and dump trucks.
Three hundred rescue workers were using heavy machinery and rescue dogs to search for the miners, state media said.
Li Zhongzeng, head of the town of Alxa League, said the rescue mission was difficult due to the threat of more landslides.
Rescue plans include layered excavation and trapezoidal descending methods from both sides of the mountain, CCTV News said on Friday.
The mine, once underground, was converted to an open-pit operation in 2012, according to state media.
It had suspended production for three years before restarting in April 2021, state media said, without specifying the cause of the closure.
Coal is a major source of energy in China but its mines are among the world's deadliest, largely due to lax enforcement of safety standards, despite repeated government orders for improvements in safety.
Authorities ordered mines in several major mining regions to conduct safety inspections after the Alxa League accident.
