Eighteen people were killed after a bus carrying university students overturned in Brazil's Sao Paulo state, the media reported.The accident occurred along a highway linking the cities of Mogi das Cruzes and Bertioga, Brazilian news agency Globo reported on Thursday.According to reports, 15 passengers died on the spot, including the driver, Xinhua news agency reported.The bus was carrying 46 passengers, mainly students, when the driver lost control of the vehicle and the bus swerved out of its lane and overturned.Video footage on Globo's website showed a convoy of ambulances at the scene to take the injured to hospital.