Authorities responded to the accident on the northbound 5 Freeway at Washington Boulevard at about 11:50 a.m. Three of the buses were carrying National Guard members, while the fourth was carrying 25 jail inmates who were being transported to the Twin Towers Correctional Facility.
Police say the Los Angeles County Sheriff's Department inmate-transport bus had been rear-ended by one of three military-transport buses in a convoy, injuring eight people. Most of the injuries were minor, but one soldier was taken to a hospital by paramedics after complaining of back pain.
"We got into a little accident but everybody is perfectly fine. The injured personnel are at the hospital, they are being taken care of right now but nothing serious," said California National Guard Lt. Michael Han.
The roughly 100 soldiers who were heading to a camp in San Luis Obispo were picked up by new buses to continue their journey.
The incident forced the closure of all northbound lanes for approximately one hour, as crews tended to the injured and the buses were removed from the freeway. Southbound lanes were briefly closed while sheriff's officials transferred inmates to another bus.
The freeway was completely reopened just after 2 p.m.
Authorities were trying to figure out what caused the crash.
City News Service contributed to this story.