A highway crash involving two trucks, a coach bus and a van killed 22 people and injured 13 Friday in southern China, local authorities said.

The government in Hunan province said in a statement that a flatbed truck lost control and veered into opposite lanes of traffic while dragging a smaller truck driving in the same direction. The trucks collided with an oncoming coach bus and a van, causing a fire, the statement said.

Photos posted by the official Xinhua News Agency showed the coach bus on fire with thick, black smoke rising.

It was not immediately clear what caused the flatbed truck to lose control. The provincial news office said the authorities were investigating.

Highway traffic typically gets heavier in late September as China prepares for its traditional Moon Festival and National Day holidays.