BEIJING -- Tons of coal dust, falling rocks and dangerous gas levels are the obstacles rescuers are dealing with in central China as they work to free 16 miners trapped by an explosion.
Authorities have now confirmed at least 21 miners were killed in the blast.

Rescuers tell the state-run Xinhua News Agency that they have located the trapped miners, but must clear more than 2,500 tons of coals dust from the mine shaft before they can reach them. It's not clear how far underground they are trapped or whether they are alive.

Xinhua also report that ventilation has resumed in the mining pit, but gas levels remain high. The rescuers are also working to clear chunks of coal that have fallen into the shaft.

Chinese safety officials say 276 workers were in the mine at the time of the explosion and 239 escaped.