A tunnel that stretches from a former Kentucky Fried Chicken in Arizona all the way to a home in Mexico was discovered last week by investigators, who believe the secret passageway was used for drug smuggling, KSWT reports.

Homeland Security Investigations said the tunnel was discovered on August 13, after the owner of the former KFC, Ivan Lopez, was pulled over by the San Luis Police Department. A canine unit alerted officers to two toolboxes in Lopez' truck. Inside the boxes, authorities say they found 118 kilograms of methamphetamine, six grams of cocaine, three kilograms of fentanyl, 13 kilograms of white heroin, and six kilograms of brown heroin. The fentanyl alone equaled three million dosage units, HSI's Special Agent in Charge Scott Brown said.

Earlier that day, Lopez was seen removing toolboxes from the old KFC. He is the owner of the building that once served as the fast food restaurant.

The tunnel is 22 feet deep, extending 590 feet long. It ends at a home in Mexico. Homeland Security Investigations and Yuma Sector Border Patrol

Agents executed a search warrant at the former restaurant and Lopez's residence. When investigating the old KFC, agents found the entrance of the tunnel in the kitchen area. It is eight inches in diameter, 22 feet deep and extended 590 feet long, HSI officials said. It ends at a residence in San Luis Rio Colorado, Sonora, Mexico.

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At the Mexican side, the tunnel exited through a trap door underneath a bed. Authorities believe the narcotics being smuggled through the tunnel were being pulled up with a rope.