The theft, estimated at nearly $400,000, occurred in the small Central Valley town of Escalon.
Investigators say it was one of the biggest to hit the booming industry. Last month, about 12,000 pounds of walnuts worth $50,000 were stolen from a trailer parked on Highway 99 north of Sacramento.
This time several truckloads of walnuts were taken from the facility. Authorities say rising prices - about $2 per pound - is what appears to be driving the recent walnut thefts.
No arrests have yet been made.
Walnuts are California's fourth-leading agricultural export. China remains the world's leading producer of walnuts
