At least four people were killed in a five-vehicle collision on a highway in the western US state of California, the state highway patrol authorities said on Saturday.Six others were injured in the serious crash involving five vehicles late Saturday night in San Pablo city, about 23 km northeast of San Francisco on the western US coast, California Highway Patrol (CHP) Oakland Area Office tweeted, Xinhua news agency reported.The wounded were transported to a local hospital for treatment, according to the CHP Oakland.It added that all westbound traffic on the highway was diverted to nearby exits and it was not known how long the duration of road closure will last.Other details about the collision including information about the victims were not immediately known.It was the second fatal traffic accident in San Francisco in two days during the Thanksgiving holiday weekend.A 35-year-old Oakland man was killed Friday after his truck hit an overpass pillar on the same interstate highway.