Chinese state media say 17 people are now dead in a coal mine explosion in southwestern China.

The official Xinhua news agency said three mine workers died in hospital and another body was recovered from the mine on Wednesday. It said 11 other miners are receiving treatment in a hospital.

Workplace safety officials said the Tuesday morning explosion was caused by a buildup of unidentified gases in the mine, located in Guizhou province.

Official Chen Fuqing said the gases were highly concentrated, accounting for the high death toll. But he said no effort was spared in the rescue operation.

Xinhua said officials are investigating the cause of the accident, the latest in a long series of fatal mining incidents.

Official data shows more than 2,400 people were killed in Chinese mining accidents last year, and labor rights groups say many more deaths may have gone unreported.