A gas leak at a coal mine in northeast China has killed 12 miners, state media reported Monday. The accident happened Sunday at a mine in the Jilin province city of Baishan, the official Xinhua News Agency said. Rescuers brought one injured person to a hospital and confirmed Monday morning that the other 12 trapped miners were dead. The cause of the accident in under investigation. Carbon monoxide is typically the main component of noxious gases that leak from coal deposits, and they must be dispersed before poisoning miners or exploding. China's mines had long been the world's deadliest, but safety improvements have reduced deaths in recent years. China plans to close scores of mines in regions such as Jilin to reduce overcapacity in the steel and coal industries, causing the loss of hundreds of thousands of jobs.