The crash happened on the southbound side of the 405 Freeway at Victory Boulevard in Van Nuys just before 10 p.m.
Authorities say three LAPD officers and some witnesses rescued a driver out of a burning car. He was rushed to the hospital and remains in critical condition.
The CHP says as many as seven other vehicles crashed while trying to avoid the original accident.
According to the preliminary investigation, the crash occurred after a Toyota Echo "for unknown reasons" became disabled and stopped in the carpool lane.
A Mercedes-Benz stopped behind the Toyota, and a 1994 Nissan Altima stopped behind the Mercedes. That's when a 2007 Mazda slammed into the Nissan, pushing it into the Mercedes.
The Nissan -- occupied by the teenage girl and the 52-year-old man -- caught fire, The teen died, and the man was badly burned, the CHP reported.
The driver of the Mazda suffered minor injuries, and his passenger suffered a fractured leg and foot. The Mercedes driver was unhurt.
"It was determined that alcohol and/or drugs were not a factor," Van Dyk said.
Four southbound lanes were closed until about 2:15 a.m., the CHP reported.