At least 35 people were killed in a fire that reduced a tour bus to ashes and a twisted frame on Sunday morning in China's Hunan province, authorities said.The bus carried 55 persons, a government official said. At least 11 persons were hospitalised and four of them were in critical conditions, Xinhua news agency reported.The accident occurred when the bus crashed into the guardrail on a highway in Yizhang county.The ensuing oil leak caused the fire, according to the government.A photo taken at the site shows huge clouds of black smoke rising from the vehicle, and another shows the black skeletons of the bus after fire was put out.State Councillor Guo Shengkun, who is also public security minister, has ordered all-out efforts to save the injured and to take measures to prevent similar tragedies in the future.The police has detained the driver.