Authorities said a 20-year-old, a 16-year-old and a 14-year-old, all brothers, were in the big rig at the time of the crash with their 3-year-old nephew. The 14-year-old initially fled the scene with the 3-year-old, but they were found a short time later.
The 20-year-old man initially said he was driving, but CHP investigators believe that the 16-year-old took the wheel when his older brother got tired.
CHP Officer Ming Hsu said the 20-year-old was the only one licensed to drive the big rig.
"He should have been the only one driving the vehicle," Hsu said. "At this point, he still claims that he was driving the vehicle, but the 16-year-old has said he was driving, and the evidence supports the 16-year-old's claim."
Residents say if the trees weren't there, the truck would have barreled right into the mobile homes at the base of the embankment. Homeowner Mark Leon said his home was nearly taken out by the big rig - it came to rest just 15 feet away.
Leon said he has lived in his home for 25 years, and the same type of accident happened about nine years. He says he's been trying to get the state to build a concrete barrier here for years.
"They need to put a guard rail up there with some steel, rebar and concrete, not this Mickey Mouse stuff you see," said homeowner Mark Leon. "What is it going to take, to wipe a house out, to wipe a family out?"
No one was seriously hurt in crash, though the trailer was heavily damaged and spilled its 36,000-pound load of whipped cream on the embankment.
Police said the young boy was not in a child seat. The parents of the 3-year-old are heading down from Modesto to pick up their child. No one has been arrested, and no charges have been filed, but the CHP said it is still investigating.
The 20-year-old male and the 16-year-old male were treated for minor injuries.
The accident caused traffic delays for eastbound traffic during the morning commute.
The Associated Press contributed to this story.