Four people were killed and nine others reported missing in a coal mine accident in China's Guizhou province, authorities said on Tuesday.The accident took place at around 9.10 p.m. on Monday at the Zimujia coal mine in Panzhou city, reports Xinhua news agency.Rescue work is underway.Chinese mines, especially coal mines - the country's main source of energy, have a high accident rate and are among the most dangerous in the world, although in recent years the number of fatal accidents has fallen significantly.In 2017, there were 219 accidents in Chinese coal mines with 375 deaths, a drop of 28.7 per cent on the death toll of 2016 and 20 times lower than the figure recorded during the early 2000s, when up to 7,000 people fell victim to mine accidents each year.