Firefighters conduct a rescue operation at the site of an accident during which a bus fell into a ravine in the Daxian County of Dazhou City, southwest China's Sichuan Province, Dec. 20, 2012. Five people were killed and 28 injured in the accident which occurred at about 9:30 a.m. on Thursday when a bus broke through a guardrail and overturned off a 50-meter-deep ravine in the Daxian County. An investigation into the cause of the accident is under way. (Xinhua)