The incident took place at 3:50 pm local time (0750 GMT) on Wednesday at a coal mine on the outskirts of Jixi city in Heilongjiang province, state broadcaster CCTV said.
The accident -- which involved a vehicle in the mine's inclined shaft -- "caused 12 deaths and injured 13, and the injured have all been sent to hospital for treatment", CCTV said on Thursday.
"The cause of the accident is still under investigation," CCTV said.
Mining safety in China has improved in recent decades, as has media coverage of major incidents, many of which were once overlooked.
But accidents are still common in an industry with a poor safety record and where regulations are not necessarily enforced.
Last year, 245 people died in 168 accidents, according to official figures.
In November, an accident at another coal mine in Heilongjiang killed 11 people.
In September, at least 16 people were killed in a coal mine fire in southwest China's Guizhou province.
In February, a coal mine partly collapsed in the remote and sparsely populated Alxa League of the northern Inner Mongolia region after a 180-metre-high (590-foot) slope gave way.
Dozens of people and vehicles were buried under a mountain of debris, but authorities did not disclose the final death toll for months.
It was only revealed in June that 53 people had been killed.
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