The collision was reported at 1:53 a.m. near Van Nuys Boulevard, according to the California Highway Patrol.
A man in his late 20s was pronounced dead at the scene, the CHP said. It was unclear how many others were possibly injured.
SIGALERT CANCELLATION IN ARLETA: NB I-5 AT VAN NUYS BLVD., ALL LANES ARE OPEN— CHP PIO - LA County (@CHPsouthern) January 26, 2017
The southbound side was reopened by 2:30 a.m. Northbound traffic was diverted onto Van Nuys Boulevard until shortly before 5:30 a.m., when the SigAlert was canceled and all lanes reopened.
City News Service contributed to this report.