TAIYUAN - Six junior high students were killed and another six injured after a minivan taking them to school was rear-ended by a truck in North China's Shanxi province early on Monday, local authorities said.

The van, which is allowed to carry a maximum of seven passengers, had 12 people on board when it was hit by a heavy truck from behind at about 6:50 am, said a spokesperson with the city government of Jiexiu.

The van was taking students from Lengquan Village to a middle school in town a dozen kilometers away.

Four boys sitting on the backseat died at the scene and another two passengers, a boy and a girl, died in hospital later, said the spokesperson.

The accident injured another six passengers in the van, and three are still in critical condition.

Police have the truck's owner in custody, but are still looking for the truck's driver as he fled the scene of the accident, according to the spokesperson.

The cause of the accident is under investigation.