BEIJING  - At least 18 people were killed, including one child, after a speeding, overloaded tourist bus veered off an icy highway bridge in southwest China, local authorities said Thursday. The 53-seat bus -- packed with 57 people -- plunged off the bridge in Guizhou province on Wednesday, leaving six others in critical condition, a spokeswoman for the local government told AFP. The injured were rushed to a local hospital and an investigation into the cause of the accident -- which happened in Guiding county -- has been launched. The spokeswoman for the Guiding government, said one of the four extra people travelling on the bus.