GUIYANG - Three people were killed and four others were injured after a truck and an ambulance collided Wednesday morning on an expressway in Xiuwen county in Southwest China's Guizhou province.

The truck collided with the ambulance at about 6 am on a section of the Guizhou-Bijie expressway, sources said.

The injured have been rushed to hospital. The identities and conditions of the casualties are not yet known.

An investigation is under way.