At least 12 people were killed in an expressway accident in China's Henan province on Friday, authorities said.The accident happened shortly after midnight on an inter-provincial expressway in Xinxian county, the Global Times reported.The authorities said a bus had toppled on the slippery road and a truck crashed into the bus.Nine people were confirmed dead at the scene and three others died later in the hospital.Nineteen people were still in hospital and in stable condition.Police have detained the drivers for investigation.