The wreck occurred on the southbound 605 Freeway at Rose Hills Road around 2 a.m.
Several cars were involved in the crash.
A total of seven people were taken to local trauma centers, officials said.
One person was pronounced dead. Six others were hurt - four of them were listed in critical condition.
SIGALERT ISSUED IN PICO RIVERA: SB I-605 AT ROSE HILLS, HOV AND #1/2/3 LANES WILL BE CLOSED UNTIL FURTHER NOTICE DUE TO A TRAFFIC COLLISION— CHP PIO - LA County (@CHPsouthern) August 13, 2017
The southbound lanes were shut down following the crash. Lanes began gradually reopening later in the morning.