Earlier reports suggested that 14 people had been killed and 34 others injured.
The Xinhua news agency specified that 10 injured persons are currently in critical condition.
The accident occurred on Saturday, at around 7:20 p.m. local time (11:20 GMT) at a toll station on a highway connecting Gansu's capital of Lanzhou and Hainan province's capital of Haikou. The driver of a semi truck lost control of the vehicle and crashed into a line of 31 vehicles.
The police have already detained the driver, who was slightly injured. He said that the brakes on his truck had failed.