State broadcaster CCTV said the incident occurred at around 10:00 am (0200 GMT) as workers were closing a ventilation shaft at a coal mine in the city of Leshan, Sichuan province.
The outlet did not give details of what happened but said the accident left a total of eight people dead, revising up an earlier toll of seven.
It said that rescue operations had been concluded.
Mine safety in China has improved in recent decades, as has media coverage of major incidents, many of which were once overlooked.
But accidents still occur frequently in an industry where safety protocols are often lax, especially at the most rudimentary sites.
A major disaster happened in February last year when a slope at an open-pit coal mine in the northern Inner Mongolia region suddenly collapsed, burying dozens of people and vehicles.
State media later reported an official as saying 53 people were dead or unaccounted for when search and rescue work concluded two weeks later.
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