Heavy fog caused serious road accidents on a section of the Beijing-Shanghai Expressway in Tai'an, Shandong province, at about 7 am on Monday, CCTV reported.

More than 30 vehicles were involved in a series of pileups on a 10-kilometer stretch of the expressway near Dawenhe Bridge in Tai'an.

Rescue work started at 7:30 am, after local firefighters received an emergency call, and was completed by midday.

The number of casualties is still unknown and an investigation has been launched.

Police warned drivers to be extra careful in foggy conditions.