Two miners managed to escape from the Jinshangou coal mine in Chongqing municipality, where firefighters and militia members were digging through tunnels blocked by debris after Monday's blast, state broadcaster CCTV said.

"The rescue team has carried out three underground operations so far," Chongqing deputy mayor Mu Huaping told a press conference on Tuesday, CCTV said.

"We have found that some tunnels have collapsed and the amount of poisonous gas has exceeded the alarm level at some parts," he said.

Chongqing officials ordered the temporary closure of some coal mines in the area while investigators look into the accident at the Jinshangou mine, the official Xinhua news agency said.

Coal accounts for almost two-thirds of China's energy consumption, but its mines are among the world's deadliest, due to lax enforcement of safety standards.