All lanes of eastbound Highway 4 in Antioch are open Tuesday afternoon after a big-rig overturned on the freeway, blocking lanes for several hours.

The Contra Costa office of the California Highway Patrol first reported the big-rig blocked the left three lanes of the freeway near the Contra Loma Blvd. exit around 8:50 a.m. 

In an update posted shortly before 10 a.m., the agency said the left-three lanes were still closed, while the rightmost lane was open. All eastbound lanes of the freeway, a crucial link for commuters in Eastern Contra Costa County, were reopened around 12:30 p.m.

Officials did not say what caused the big-rig to overturn.