A tunnel that was used for drug smuggling between Mexico and Arizona was discovered last week and investigators gave new details about the case on Wednesday.

[VIDEO: Inside a drug-smuggling tunnel at Arizona-Mexico border]

The tunnel is 22 feet deep and extends to 590 feet long, according to Homeland Security and Yuma Border Patrol. The tunnel went from a home in San Luis Rio Colorado, Sonora, Mexico, to a former Kentucky Fried Chicken in San Luis, Arizona.

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[RELATED: Border Patrol find abandoned cross-border tunnel in Douglas (April 28, 2017)]

Investigators said the tunnel was discovered after the San Luis Police Department pulled over Ivan Lopez on Aug. 13.

Police say they found a wide range of drugs in his truck.

[RELATED: 2 arrested in Arizona in cross-border tunnel investigation (March 24, 2016)]

"[He had] over 118 kilograms of methamphetamine, over six kilograms of cocaine, over three kilograms of fentanyl, over 13 kilograms of white heroin and over six kilograms of brown heroin," said Scott Brown, a Homeland Security Investigations special agent. "Just the three kilograms of fentanyl translates to over 3 million dosage units."

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[CBS 5 INVESTIGATES: Smugglers use drainage tunnels and sewers to deliver drugs (March 6, 2016)]

Scott said Lopez, who owner of the former KFC, had been removing toolboxes from the old KFC earlier that day.

Law enforcement then searched the KFC building and found the tunnel. Border agents said the tunnel opening at the abandoned restaurant was only 8 inches in diameter.

[RELATED: Suspected drug tunnel found near Nogales, AZ (March 29, 2016)]

Authorities believe the smugglers used a rope to pull the narcotics up from the tunnel.

An investigation is underway.

[PDF: Criminal complaint against Ivan Lopez]

[PDF: Memorandum seeking detention of Ivan Garcia]

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