Five teens were traveling in a white 1997 Chevrolet four-door, lifted pickup truck to Vacaville from Lake Berryessa around 5:20 p.m., the CHP said.
A witness told officers that the truck was traveling at high speeds south on Pleasants Valley Road where it went up the curve, according to the CHP.
The truck left the roadway continuing east just south of Chester and Pleasant Hills Ranch roads before it traveled into an open field and rolled over several times, the CHP said.
All five teens were ejected from the vehicle, according to the CHP.
A 19-year-old man suspected of driving the vehicle suffered major head trauma and was pronounced dead at the scene, the CHP said.
A 16-year-old girl was transported for major injuries to Kaiser Permanente Vacaville Medical Center where she was pronounced dead around 10:15 p.m., the CHP said.
A 17-year-old girl was also taken to Kaiser Permanente Vacaville Medical Center for major abrasions and fractures to her spine, right arm and left ankle, according to the CHP.
Emergency crews airlifted a 16-year-old boy to the University of California at Davis Medical Center in Sacramento for major head and internal injuries, the CHP said.
An 18-year-old girl was also airlifted to NorthBay Medical Center in Fairfield for a fractured spine, ruptured spleen and collapsed lung.
CHP investigators do not believe any of the teens were wearing seatbelts at the time of the crash and say alcohol may be a factor in the collision.