The death toll from a coal mine explosion in central China's Henan Province has risen to 31.

6 miners are still trapped underground, but officials say their chances of survival are very slim.

More than 2,500 tons of coal dust smothered the pit after the blast.

The accident occurred Friday morning in a pit owned by Pingyu Coal & Electric Co Ltd based in Yuzhou City. An explosion at the same mine two years ago killed 23 people.

China's mines are the deadliest in the world, due to lax safety standards. More than 2,600 people died in coal mine accidents in 2009 alone.