Four died and six others were injured - two seriously - when an overloaded three-wheel motor vehicle and a truck collided head-on early Thursday morning in northwest China's Gansu Province, local safety authorities said.

The accident happened at about 6:40 a.m. at the Jieheba section on State Highway 312, the Gansu Provincial Administration of Work Safety said in a statement.

The three-wheel vehicle was overloading nine passengers illegally when the accident happened, an initial investigation has shown.

The driver of the three-wheel vehicle and three passengers on board died at the scene, and other six passengers were injured, including two in critical condition.

A further investigation into the accident is under way.