Rescuers lifted seven injured miners to the surface from a coal mine in central China\'s Henan province on Friday after a rock burst killed four and trapped another 50, the official Xinhua News Agency reported.Six of them had sustained minor injuries, and the other one had been seriously injured when rescuers located them 510 meters underground, local rescue headquarters said, according to Xinhua.The accident happened at around 7:45 pm (1145 GMT) Thursday in the Qianqiu Coal Mine in the city of Sanmenxia. A total of 75 miners were working in the shaft at the time of the accident, of whom 14 managed to escape, the report said.The shaft is about 760-meter deep and the rock burst blocked off the shaft at a depth of about 480 meters, which has hampered ongoing rescue efforts. A 2.9-magnitude earthquake hit Sanmenxia at about 7:18 pm, and the rock burst was later reported from the shaft in the mine.The coal mine, with an annual production capacity of 2.1 million tons, belongs to a major state-owned coal enterprise in Henan.Although work safety situations in China have improved, mine disasters continue to kill many workers each year. Last year, 2,433 people were killed, according to China\'s State Administration of Coal Mine Safety. This means accidents killed six coal miners per day.