HARBIN - Rescue efforts of 11 miners who have been trapped for three days are being hampered by falling ceilings and dense concentration of inflammable gas in the shaft of a coal mine in northeast China.

On Tuesday, rescuers were still unable to reach the miners because of the falling ceilings and a high level of carbon monoxide in the coal mine shaft in Shuangyashan city, Heilongjiang province, according to a news update from the rescue headquarters.

As of 3:00 pm Tuesday, rescuers who were working in shifts cleared a 20-meter-long tunnel blocked by fallen rubble from the ceilings, but another section the same length lay ahead, it said.

The coal mine shaft was razed by a fire on Saturday, when 11 out of the 13 miners working underground were trapped. The other two miners managed to get out of the pit.

The high density of the carbon monoxide, which increased the temperature in the shaft to 45 degree centigrade, was also hampering rescue work, according to the headquarters.

Experts, who are considering a new rescue plan, said they believe air and water access is available where the miners are, and it is possible that they are still alive.

The cause of the accident is still under investigation.