At least five big rigs overturned Wednesday near the intersection of the 15 and 10 freeways in the Fontana area.
A SigAlert was issued near the interchange.
Another truck toppled onto its side on a Fontana street
Strong Santa Ana winds were expected to reach 70 miles per hour Wednesday across much of Los Angeles County.
Gusts up to 80 mph are possible, according to the National Weather Service.
"It should really peak between 6 a.m. and 3 p.m. today,'' Dave Bruno of the National Weather Service said in a telephone interview. ``It's definitely a typical Santa Ana event. We're not as dry as a typical October. We've had a lot of rain to green things up. But it has been dry lately and we do have high wind warnings in effect."
Wind gusts were already topping 60 mph in parts of the San Gabriel Mountains by 5:30 a.m., according to the Weather Service.
Between 1:30 p.m. Tuesday and 5:30 a.m. Wednesday, gusts of 66 mph were measured at Chilao, 44 mph at Leo Carrillo Beach, 61 mph in the Malibu Hills, and 42 mph in Newhall Pass.
The driving force behind the Santa Anas -- as usual -- is a high- pressure system building over the Great Basin area northeast of Southern California.
Vulnerable areas in L.A. County Wednesday include the Antelope, Santa Clarita and San Fernando valleys, where wind gusts to 60 mph and stronger will be capable of knocking down trees and power lines, according to the Weather Service.