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Antidrug officials in the Northwest have discovered that marijuana growers are cultivating and concealing illegal crops on a large scale among grapevines in Washington state.

Since July 8, law-enforcement agencies in Washington's Yakima Valley have seized from the region's vineyards more than 200,000 marijuana plants, with an estimated street value of more than $165 million. The agencies say they expect to find more of the plants in vineyards as the marijuana-growing season nears its conclusion in late September. The Yakima Valley is about 150 miles southeast of Seattle.

Police say they believe Mexican cartels are tapping into networks of Hispanic immigrant workers who go to the Yakima Valley to pick fruits and vegetables.

In most cases, vineyard owners weren't aware of the illegal farming operations, said Washington state Patrol Sgt. Rick Beghtol, s upervisor for a multiagency antidrug task force. Many vineyard owners don't tend their vines, instead contracting with migrant workers and small cultivation and harvesting companies, he said. This year, law-enforcement agencies have raided 13 vineyard operations and arrested 33 suspects, all of them Hispanic immigrant workers, he said. Most were caught on the premises, he said.