Big Rig Overturns, All Lanes Cleared on Westbound Hwy 4 in Antioch

State Highway 4 in Antioch reopened after a big rig overturned and was blocking all lanes Saturday morning, 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 collision was cleared around 11:15 a.m., the CHP said.

The cause of the collision remains under investigation.