A transportation broker tipped sheriff's deputies that something seemed amiss. They arrested Martinez, who told them he was supposed to drive the load to a specified address in Los Angeles, park it and walk away.

The trucking firm that hired him turned out to be a fake. The company's logo was merely taped onto the side of the truck, and it had stolen license plates. Martinez pleaded guilty in December to commercial burglary and possession of fake identification. He was sentenced to 350 days in jail and three years of probation.

Authorities say this type of industrial identity theft, known as a "fictitious pickup," is becoming more sophisticated. It often involves con artists providing fabricated insurance documents and U.S. Department of Transportation numbers for trucks.

The driver presents the paperwork to the unsuspecting nut processor.

A walnut farmer suspected he had fallen victim to such a crime in March after a $250,000 load left his yard, so he called Detectives Pat McNelis and Matt Calkins at the Butte County sheriff's department. The detectives traced phone records to Los Angeles, where police there served search warrants and seized evidence. The investigation continues, detectives said.

"In our case, there's multiple levels of people that were involved in a complex crime," Calkins said. "This is an organized criminal enterprise. It's not one or two people acting on their own."

The California Highway Patrol investigates cargo thefts, but doesn't tally nut thefts separately. The CHP hasn't established a link between such thefts and any specific criminal organization, spokeswoman Erin Komatsubara said.

Growers and nut processors say they have been so hard hit in the past year that a coalition of nut associations formed a task force in October to seek the advice of law enforcement and to create an eight-step checklist for growers and nut processors.

The list includes fingerprinting drivers, taking their photos and calling the broker to confirm that the paperwork is legitimate. Such common-sense steps can save hundreds of thousands of dollars in vanishing cargo, said Carl Eidsath, a task force member representing the California Walnut Board.

Too often, Eidsath said, the theft isn't detected until it's too late. "The only reason they knew something wasn't right was when the load didn't show up at the customer," he said. "That's days and days later."

Taking additional safeguards, almond grower Michael Fondse, the fourth generation at Fondse Brothers behind his father, Kevin Fondse, said he planted a row of redwood trees along the road to create a visual barrier, hiding his orchards from would-be thieves, and he installed cameras at the processing plant.

"We've installed a lot of lights," he said. "That's the No. 1 deterrent, keeping everything bright."

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