Dense fog caused several collisions on a road in China.

Footage shows the massive car pile-up near the exit of S3 Hufeng Expressway in Shanghai on January 4.

Vehicles collided with one another at five different points on both the up and down lanes along the busy road that had been obscured by thick fog.

A total of 21 vehicles suffered damages in the accidents, local media reported.

Video footage captured after the impact shows several vehicles lying across the expressway, a lorry overturned, and several small cars and vans collided, with a large amount of debris scattered on the scene.

Some vehicles had individuals trapped inside. Traffic police, fire, medical, and road management rescue departments were also at the scene, trying to clear up the site.

Due to the large number of vehicles involved in each crash, the rescues took a considerable amount of time. Fortunately, there were no casualties.

The road was jammed up until 10:30 am, local media reported.

A driver at the scene reported that the traffic flow had started moving around 10:14 am. Police later reminded all motorists: 'In case of heavy fog, drivers are urged to reduce speed, maintain a safe following distance, turn on tail lights, and drive cautiously to ensure safety on the expressway.'