Chinese officials said Friday that four people have been confirmed dead and 50 are missing after a failure of rock inside a coal mine in central China's Henan Province.
Officials say the accident happened Thursday evening in the Qianqiu Coal Mine in the city of Sanmenxia.
A total of 75 miners were at work at the time of the accident. Fourteen miners managed to escape, and seven were rescued. Chinese state media said one of the seven was seriously hurt.
Officials say rescue efforts are underway and there is a chance that some of the missing miners could have survived.
A rock failure of this nature, technically known as a rock burst, occurs when rock under high pressure suddenly releases its energy in a violent explosion. The cave-in took place shortly after a magnitude 2.9 earthquake struck Sanmenxia.
Last Sunday a gas explosion at a coal mine in Hunan province killed 29 workers.
China's coal mines are the deadliest in the world, due to poor compliance with safety standards. In 2010, China reported that 2,433 people died in coal mining accidents, although that number is an improvement over earlier years.
Some information for this report was provided by AP, AFP and Reuters.