China says at least 13 workers have been killed and another five people are missing, after an apparent gas explosion Tuesday in a coal mine in the southwestern province of Guizhou.

The official Xinhua news agency says another 13 miners managed to escape, and that an investigation is under way.

China's mines are among the world's deadliest, in large part because of lax security measures. Many of them operate illegally.

Official data shows more than 2,400 people were killed in accidents last year. But labor rights groups say the toll is likely much higher.