URUMQI -- Nine people were killed and seven others injured in expressway collisions on Saturday night in Northwest China's Xinjiang Uygur autonomous region, local authorities said on Sunday.

The accidents happened at around 10 pm on different sections of an expressway in the city of Usu in Tacheng Prefecture, where multiple vehicles crashed in succession. In total, five large vehicles and seven smaller cars were involved.

The injured were rushed to hospital for emergency treatment.

Local officials said the crashes happened amid sudden heavy fog, combined with sub-zero nighttime temperatures that caused road surfaces to become wet and icy within a short period of time.

Further investigation into the accidents is underway.