Updated

Authorities in California are trying to crack the case of a nut thief who made off with 140,000 pounds of walnuts.

The theft, estimated at nearly $400,000, occurred Sunday 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.