The blast hit the No. 2 Port Mine at Xuancheng in Anhui province last Wednesday, when 45 people were working in a shaft 450 metres below ground, a mine official said.
Ten miners died instantly after a spark from mining equipment
ignited underground gas, the official said.
Two more miners died in a local hospital, where 10 others remained, he said.
Accidents kill up to 10,000 miners annually, according to government statistics.
Poor safety and overworking were the main causes of an explosion that killed 162 miners at a large state-run coal mine in Guizhou province, southwest China, on September 27, the official China Youth Daily reported on Monday.
The Muchonggou coal mine violated many safety regulations and introduced a strict work regime in an attempt to turn around 28 years of losses, the newspaper quoted officials investigating the cause of the blast as saying.
A ventilation system designed to extract gas from the shaft had failed and a succession of electrical faults, including bypassed fuses, made it easy for the gas to ignite, investigators said.
Last year the mine switched from a three-shift system to two shifts, requiring miners to work 12 hours per shift, and made a profit of 1.8 million yuan (220,000 dollars) in the first half of this year, the newspaper said.
China also has hundreds of illegal mines where safety standards are generally much lower than in state-run mines.
Local officials often delay or fail to report mine deaths, with some areas underreporting accidents by as much as 85 per cent last year, state media said.
(la/dpa)