The Ford Edge crashed around 3:15 a.m. at the southbound Lincoln Avenue off-ramp of the freeway, according to the California Highway Patrol.
"For an unknown reason, the Ford veered off the road and struck a wood/metal guardrail, and a concrete pillar," the CHP said in a news release. "The Ford then continued southbound and collided with a sloped concrete embankment and overturned before finally coming to rest in a vegetation covered embankment."
2 killed, 2 others injured in off-ramp crash on southbound 5 Freeway in Anaheim
Two of the teens in the vehicle died at the scene, the news release said. Two others were rushed to an area hospital, where one was later pronounced dead.
The deceased were not immediately identified.
According to investigators, apparently none of the occupants were wearing a seat belt.
A witness reported that the driver of a white SUV appeared to miss the off-ramp and lost control while making a late attempt to take the exit, according to a CHP incident log.
The vehicle flew over the side at high speed and two of the teens were ejected, the log said.
"Drugs and or alcohol have not been ruled out as a factor in this crash," the Highway Patrol said in a statement.
City News Service contributed to this report.