Lanes on the southbound 5 Freeway were closed throughout Tuesday morning in the Sylmar area after a big rig crash.
The road reopened at about noon near the Roxford Street exit.
CHP Officer Patrick Kimball said the big rig flipped on its side Tuesday at about 4 a.m. Traffic began building quickly, causing gridlock on the 5 and 14 freeways about 30 miles north of downtown Los Angeles. The big rig was carrying a load of cardboard, according to the CHP.
There's also a diesel spill. Two tow trucks pulled the vehicle to an upright position.
There were no reports of injuries.