SAN RAMON (CBS SF) — Two people were killed, and two others injured in a fiery crash on Interstate Highway 680 in San Ramon early Sunday morning, the California Highway Patrol said.

CHP investigators said a Volkswagen Jetta was southbound on I-680, north of Alcosta Boulevard, around 3:30 a.m. when it went off the roadway to the right and then swerved back and hit the center median.

READ MORE: Peloton Tread+ Owners Told to Stop Using Treadmill in 'Urgent Warning' From Gov't Agency

The Jetta stopped sideways, blocking the left lane.

It was then struck by a Ford Fiesta, causing major damage to both cars and starting a fire that engulfed the Jetta, killing two people trapped inside.

READ MORE: Father, Child Die In Early Morning Oakland Fire; Deaths Being Investigated As Homicides

“When officers were responding, one vehicle was on fire,” said CHP Sgt. Andrew Murphy.

A third person in the Jetta suffered major injuries and the driver of the Fiesta had moderate injuries. Both were taken to John Muir Medical Center in Walnut Creek.

The crash closed the freeway for more than an hour, the CHP said.

MORE NEWS: Woman Dies in Saturday-Morning Rollover Crash on I-580 in Oakland

Anyone who witnessed the collision is asked to call the Dublin office of the CHP at (925) 828-0466. The crash remains under investigation.