The accident in the coal mine in the city of Sanmenxia in Henan province occurred Thursday evening when 75 miners were working in the shaft, the official Xinhua News Agency said. Fourteen workers escaped.
At least 200 workers were digging a small rescue tunnel about 1,650 feet (500 meters) deep to try to reach the trapped miners, the People's Daily newspaper's website said.
The Qianqiu Coal Mine belongs to Yima Coal Group, a large state-owned coal company in Henan, the State Administration of Work Safety said on its website.
Xinhua said a magnitude-2.9 earthquake occurred to the east of Sanmenxia and that the rock explosion happened about 30 minutes later.
The phenomenon known as a "rock burst" occurs when settling layers of earth bear down on the walls of a mine and result in a sudden, catastrophic release of stored energy. Exploding pillars can turn chunks of rock or coal into deadly missiles, and the shock waves alone can be lethal.
The survival of the trapped miners depends on the intensity of the rock explosion and the rescuers' ability to provide ventilation to them, a local official told The Associated Press.
"If it was not very strong, it might have caused the tunnel to get narrower, but we might still be able to send some air in there to ensure ventilation," said the Yima city Communist Party's head of propaganda, who would give only his surname, Tian, as is common with Chinese officials.
"But if the impact was pretty strong and caused the tunnel walls to collapse, then the ventilation was probably cut off immediately, suffocating the people trapped there. In that case it would be hard to rescue them," Tian said.
Tian said it was difficult to determine how deep in the mine the trapped workers were.
According to Xinhua, workers were digging a tunnel about 830 yards (760 meters) long, but after the rock burst, the tunnel appeared to have "basically folded" a little more than halfway down the passage, at 525 yards (480 meters). It was unclear what the condition of the tunnel was beyond that point, Xinhua said.
China's coal mines are the most dangerous in the world, although the industry's safety record has improved in recent years as smaller, illegal mines have been closed. Annual fatalities are now about one-third of the high of nearly 7,000 in 2002.
