NANJING - A chain of accidents involving 21 vehicles killed two people and injured six others Saturday morning on a fog-engulfed expressway in East China's Jiangsu province, police and witnesses said.

Most of the accidents were pileups or rear-end collisions reported around 8:20 am on an expressway between the city of Changzhou and the provincial capital of Nanjing, according to a traffic officer in Nanjing who participated in rescue efforts.

The road is part of an interprovincial expressway that links Changchun in Northeast China's Jilin province with Shenzhen, a southern boom city bordering Hong Kong.

The officer said four of the injured are under medical observation, while the other two suffered slight injuries and have been allowed to leave the hospital.

A witness who declined to be named said heavy fog reduced visibility to around 20 meters on the expressway Saturday morning.

"Traffic was at a standstill and vehicles lined up for several hundred meters along the expressway," the witness said.

As of midday, traffic had resumed on two of the expressway's four lanes, while police are still working to open the other two.