A crash involving a FedEx truck is blocking northbound lanes of Highway 99 at Dillard Road, just south of Elk Grove.
The CHP first reported the crash at 7:30 a.m. Traffic in both directions was affected.
Hazmat crews were called to the scene to clear an apparent fuel spill.
It was not immediately known if the driver was hurt, or when the scene would clear, but signs alerting drivers to the accident were activated in Stockton.
The crash was finally cleared shortly after 3:30 p.m.