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.
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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.