BEIJING, Sept 23 (Reuters) - A fire at a coal mine in northern China has trapped 15 workers and has been burning since Wednesday, the official Xinhua news agency said. Rescuers at the mine in Shanxi province have already found three bodies, though 18 people managed to escape, the report on Sunday said. "It is not clear whether the 15 trapped miners are still alive or not, and the fire is yet to be quenched," it quoted Wang Xingui, deputy head of the rescue team, as saying. "Rescuers managed to enter the pit through another entrance on Saturday evening, but heavy smog lowered the visibility to less than three metres down in the shaft, blocking them from continuing their search," he added. The fire was likely caused by an underground cable, Xinhua said. China's coal industry is the deadliest in the world, with 2,163 miners killed in 1,320 accidents in the first seven months of 2007.