The California Highway Patrol is on scene of a crash on southbound Highway 99, just south of Pacheco Road. 

According to the CHP page, a semi collided with a vehicle just after 1:00 a.m. The semi crossed lanes and went into the center divide. 

The CHP page says the vehicle went under the big rig and both caught fire. 

All southbound lanes are blocked at this time. 

CHP says the semi was hauling 140 gallons of diesel and spilled all over the roadway. Environmental Health is arriving on scene. 

No word on injuries at this time and it's unknown when the lanes will reopen. 

We will continue to update you on this story as soon as we get more information.