All lanes of westbound state Highway 4 in Antioch are blocked this morning after a big rig overturned, according to the California Highway Patrol.
The tractor-trailer overturned at about 7:15 a.m. on Highway 4 near the Contra Loma Boulevard overpass, the CHP said.
A Sig-alert was issued at about 7:40 a.m. and the CHP has no estimated time of reopening.
The cause of the collision remains under investigation.
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