The wreck occurred near the Crown Valley Road exit around 9:15 a.m. In addition to the overturned propane tanker truck, a camper and a sedan were also involved in the crash.
The Los Angeles County Fire Department said the tanker had a slow leak. Some nearby businesses were evacuated, and a 500-foot perimeter was set up for safety, authorities said.
One southbound lane was reopened around 10:30 a.m., but the other lanes were expected to be shut down for several more hours, according to the California Highway Patrol.
SIGALERT UPDATE IN ACTON: SB SR-14 AT CROWN VALLEY RD - #1, 2, AND 3 LANES AND CROWN VALLEY RD ON-RAMP BLOCKED FOR 4 HOURS DUE TO A COLLISION— CHP PIO - LA County (@CHPsouthern) April 9, 2019
Fire officials said there were five patients total - four adults and one child. A mother and her child were airlifted to an area trauma center. Of the five patients, four were said to be in critical condition.
The cause of the crash was not immediately known.