The tunnel stretched the length of eight football fields, from a Tijuana warehouse to a San Diego warehouse, and had a rail system, lighting, electricity, and metal beams to prevent a cave-in.
Authorities confiscated at least 12 tonnes of marijuana with a street value of USD six million and arrested 22 people in San Diego and Tijuana in connection with the one of the largest tunnels uncovered in recent years.
"We see a super tunnel open for business once every year or so," US Attorney Laura Duffy of Southern California said in a statement. "Just when traffickers think they're ready to move, we put them out of business."
The San Diego end of the tunnel is located just a half- mile from the Otay Mesa border crossing.
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On Wednesday, the defendants told the undercover agent about moving loads of marijuana from the tunnel warehouse to another warehouse.
Authorities believe this would have been the first time that a significant amount of drugs would have been moved through the tunnel, CNN reported.
The tunnel is the tenth large-scale drug smuggling tunnel discovered in the San Diego area since 2006.
In all, authorities have found more than 75 cross-border smuggling tunnels, mostly in California and Arizona, prosecutors said.