California Highway Patrol Sgt. Jeff Page said the driver of a big-rig traveling west on Interstate Highway 80 exited at Columbus Parkway at about 7:15 a.m. and failed to negotiate a curve.
The big-rig struck a dirt embankment and caught fire, Page said. Another vehicle may have been involved, he said.
At least one fatality has been reported, Page said.
Access to Columbus Parkway from eastbound state Highway 37 and westbound I-80 in Vallejo is blocked for several hours.
A Sig-alert was issued just before 8 a.m.
