Six miners who survived a gas explosion that killed 22 colleagues at a coal mine in Chongqing were still receiving medical treatment on Wednesday.

Two were in critical condition and four had slight injuries, the Chongqing Administration of Coal Mine Safety said.

The accident happened at 5:40 pm on Tuesday at Nantong Mineral, a coal production company under Chongqing Energy Investment Corp, a State-owned enterprise in Wansheng district.

Twenty-eight miners were underground at the time. Five managed to escape immediately after the explosion and one later, but the remaining miners died after being trapped underground, the city's coal and mineral safety bureau said.

The survivors were taken to a hospital affiliated with the Nantong mineral bureau.

Wang Shu, an official at the hospital, said: "The four survivors who escaped with minor injuries are being treated in the respiratory department. They have dizziness and a lack of strength, mainly because they breathed in poisonous gas underground after the blast.

"The other two miners, who are burned on more than 40 percent of their bodies, are in the intensive care unit."

He Xiaogang, who was slightly injured, said he was about 100 meters above the explosion scene when the blast happened.

"When I heard the explosion, I immediately ran. The smoke was spreading quickly and I saw two miners shouting for help about 100 meters away from us," he said. The pair were later rescued.

He, 40, who comes from Chongqing, has worked at the mine for 10 years. "The mine has stressed safety issues. But we had not practiced escape drills before," He said, adding that he was rescued by emergency team members after running for about 100 meters.

Local government officials began rescue efforts immediately after the explosion, led by Chongqing Mayor Huang Qifan.

The mining group said all its seven coal mines had suspended operations. The cause of the accident is being investigated by the local government.

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Tan Yingzi contributed to this story.