The crash was reported at 8:34 p.m. on westbound Highway 4 near the Alhambra Avenue off-ramp.
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At least three vehicles were involved and one person was killed.
Contra Costa County Fire Protection District officials said one other person suffered moderate injuries and a third suffered minor injuries in the crash.
All lanes of the highway are blocked as of 9 p.m. and there was no estimate for when they will be reopened, Ogilvie said.
The CHP is diverting westbound traffic off the highway at Alhambra Avenue.