Four years after legal recreational marijuana went on sale in Colorado, Gov. John Hickenlooper says the black market for marijuana in the state is shrinking and predicted that it "will be largely gone" in a few years.
But new statistics show that arrests for the production of black market pot increased by 380 percent in the 2014-16 time frame, and Colorado law enforcement agencies say they are battling a boom in illegal marijuana cultivation by sometimes violent groups of criminals who rake in millions of dollars by exporting what they grow.
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