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With the rate of opioid addiction surging in the United States, Mexico has become the world's third-largest producer of opium, a substance derived from poppy plants that can be processed into heroin. Mexican cartels are now the primary suppliers of heroin to users in the US, and their product is mostly a crude and unrefined form of the drug called black tar.

VICE News travels to poppy plantations in the fertile mountains of western Mexico and follows the path of black tar heroin as it is trafficked across the US border to see the human cost of this lucrative but destructive trade.

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