Firefighters help the trapped get out of a car after a road accident in east China's Shanghai, Jan. 30, 2014. An 11-vehicle pileup happened on the Shanghai-Kunming Expressway Thursday morning. At least three people were killed and 15 others injured, one of whom critically, according to police. [Photo: Xinhua]

At least three people were killed and 15 others injured in an 11-vehicle pileup on a Shanghai expressway on Thursday morning.

One of those injured is in a critical condition, according to police.

The accident happened at around 7:30 a.m. about a kilometer from the Fengjing Toll Station on the Shanghai-Kunming Expressway.

Police said all of the injured have been rushed to hospital. An investigation is under way.

Shanghai was enveloped in dense fog on Thursday, the eve of Spring Festival, or China's lunar New Year, and saw heavy holiday traffic.

Witnesses said the expressway was not closed on Thursday morning, but toll collectors were advising drivers not to enter.