The blast happened as the world still was celebrating Chile's dramatically successful rescue of 33 miners trapped more than two months.
Rescuers have located the 16 Chinese miners but must clear tons of coal dust from the mine shaft to reach them, the state-run Xinhua News Agency cited a rescue spokesman as saying. It wasn't clear if the miners were alive or how far underground they were trapped.
The blast unleashed more than 2,500 tons of coal dust, an engineer for one of the mine's parent companies, Du Bo, told Xinhua. The report said ventilation has resumed in the mining pit but gas levels remain high.
The gas level inside the mine was 40 percent, far higher than the normal level of near 1 percent, China Central Television reported. The gas wasn't specified, but methane is a common cause of mine blasts, and coal dust is explosive.
The more than 70 rescuers on the scene also must clear chunks of coal loosened by the blast that fell into the shaft, the state-run broadcaster said.
Twenty bodies had been retrieved by the afternoon, Xinhua said.
China's state-run media had joined the breathless global coverage of the Chilean mine rescue, and the country's propaganda and mine officials likely will face pressure to be just as open about the progress of its rescue efforts.
China's mining industry is the most dangerous in the world - with 2,600 people killed in accidents last year - and the country's leaders have been making a high-profile push in recent years to improve mine safety. Premier Wen Jiabao has even ordered mining bosses into the mines with their workers or else risk severe punishment.
Saturday's blast at the state-run Pingyu Coal & Electric Co. Ltd mine happened as workers were drilling a hole to release pressure from a gas buildup to decrease the risk of explosions, according to the work safety administration.
State media say another gas blast at the same mine two years ago killed 23 people.
In the latest blast, 276 workers were in the mine when the explosion happened and 239 escaped, according to the state work safety administration.
The mine in the city of Yuzhou is a couple of hours outside the Henan provincial capital of Zhengzhou and about 430 miles south of Beijing.
China had its own stunning mine rescue earlier this year, when 115 miners were pulled from a flooded mine in the northern province of Shanxi after more than a week underground. The miners survived by eating sawdust, tree bark, paper and even coal. Some strapped themselves to the walls of the shafts with their belts to avoid drowning while they slept.
Mining fatalities decreased in recent years as China closed many illegal mines, but deaths increased in the first half of this year. At least 515 people have been killed nationwide in coal mines alone.
An unknown number of illegal mines still exist to profit from the fast-growing economy's huge appetite for power.
China's economy remains reliant on coal for about two-thirds of its energy needs.
By Associated Press Writer Cara Anna; AP researcher Henry Hou contributed to this report