More than 10,000 trucks mainly carrying coal are stuck in a 120km traffic jam in the northeastern Chinese region of Inner Mongolia.
State television said the highway heading towards Beijing and the neighbouring province of Hebei was now more like a car park. The jam started forming on Tuesday after traffic restrictions began being enforced in Hebei, it added.
Most of the vehicles were coal trucks, the report said, which were also blocking feeder roads leading onto the highway. But the road further into Hebei had already begun freeing up, offering hope to the drivers stuck in Inner Mongolia, it added.
China is the world's top producer and user of coal, which has fuelled its rapid economic growth over the past three decades, and Inner Mongolia has large reserves.
Just over a week ago the authorities finally cleared a previous 100km tailback that had lasted nine days.
While China is spending billions of dollars on infrastructure such as roads and railways, it is still struggling to keep up with the demands of its booming economy and traffic jams are common.