BEIJING — Rescuers battled dangerous levels of gas and the risk of falling coal as they worked to free 17 miners after an explosion at a coal mine in central China early Saturday. Officials confirmed 20 miners were killed.

The blast happened as the world still celebrated Chile's dramatically successful rescue of 33 miners trapped more than two months.

Some 276 workers were in the Chinese mine when the explosion happened and 239 escaped, according to the state work safety administration. It wasn't clear how far underground the miners were trapped or what their conditions were, including whether they are alive.

The more than 70 rescuers on the scene face two major difficulties in reaching the miners: excessive gas levels and chunks of coal loosened by the blast that fell into the shaft, according to China Central Television.

The gas level inside the mine was 40 percent, far higher than the normal level of near 1 percent, the state-run broadcaster reported. The gas wasn't specified, but methane is a common cause of mine blasts, and coal dust is explosive.

The 20 dead miners' bodies had been located and rescuers were trying to retrieve them, the report 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.

Saturday's blast at the state-run Pingyu Coal & Electric 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.

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.