The backup was stretching for miles and was not expected to be cleared anytime soon.
The truck overturned around 11 a.m. on the northbound 5 near the 134. A witness told CHP the semi appeared to have lost control and jack-knifed.
The tractor trailer has a Chiquita logo on the side. Officials say it was hauling some 30,000 pounds of restaurant equipment.
The driver was initially trapped in the cab but later freed and brought to a hospital.
Fuel spilled out over the roadway.
The CHP shut down the northbound 5 and was diverting traffic onto the 134.
By the afternoon, several lanes were reopened.
The cause of the accident remains under investigation.