The unconfirmed report of gunfire was received shortly after 10 a.m. on the freeway near Atlantic Avenue, a CHP spokesperson said. Whether any people or vehicle were struck by gunfire was unknown.
At least seven Highway Patrol vehicles were parked in the otherwise empty southbound lanes as officers scoured the freeway in search of evidence.
The CHP began reopening lanes shortly after 11 a.m., and the SigAlert was canceled.
Southbound traffic remained backed up as traffic began slowly returning to normal at the scene.