Nineteen students and a teacher were killed when a truck mowed down a group of junior high school students taking their morning exercises on a highway in Shanxi province yesterday. The victims were from Nanmiao High School in the town of Guodao, the Shanxi Communications Radio Station reported. Xinhua reported that 18 of the victims died at the scene and two in hospital. It said 17 people were being treated for their injuries, with one in critical condition. 'A thirtysomething male teacher also died. He was a class supervisor, responsible for leading the students on their jog every morning,' a female staff member from the school told the South China Morning Post. She said the school's 1,000 or so students performed compulsory exercises every morning. In winter they usually jogged along the highway. The truck ran into the students from behind as they were jogging back to school. It veered off onto a dusty road running parallel to the highway and knocked down a dozen trees before returning to the main road about 100 metres from the students. Sources said that most of the victims were in the final year of junior high school and were at the back of the exercise group. They said the teacher died while trying to prevent other students from being hit. Other teachers were among those injured. Neither school officials nor police would confirm the casualties last night, saying officials were still at the crash scene and the area had been sealed off. A police officer said the accident was the most serious in Qinyuan county's history. The officer said Qinyuan was a rich coal mining area and semi-trailers, trucks and other heavy transport vehicles regularly drove along the highway. Contributors to a Sina.com chat room said the accident had been caused by the driver of a truck from a coal mine who was exhausted after spending all night behind the wheel. In December 2001, a farming vehicle killed four students and injured two as they crossed the road from a township high school in Pingyi county, Shandong .