Take a look inside the secret border tunnel discovered south of San Diego as NBC 7 gives you exclusive access.
The so-called "super tunnel" found Wednesday night runs from a warehouse off Drucker Lane in Otay Mesa to another warehouse in Tijuana.
Most of the tunnel - some 1500 feet - has been cut on the U.S. side of the border, stretching only a few hundred feet into Mexico.
A stairwell was cut to allow entrance in to the dark, humid tunnel.
As our NBC 7 crew walked down the stairwell, they dropped about 35 to 40 feet underground.
Because the tunnel itself was no more than 3 to 4-feet high, people using the tunnel could not stand up.
The geology is mostly clay and sandstone. Markings are visible on the walls, showing the tedious and difficult work done with pick axes and other hand tools.
Agents say, unlike past tunnels they've discovered, the shoring, support structure was not as sophisticated here. It’s a good indication that whoever dug the tunnel wanted it done as quickly as possible.
There are also cables and a long plastic tube that served as a critical component.
“They must have had a fan on the other side, some sort of fan system that would pump in some fresh air and the tube would be the mechanism for which delivers that air,” said Joe Garcia, Department of Homeland Security Investigations.
Several hundred feet from where it ends on the U.S. side, tracks that are part of a rail system are visible. Smugglers likely used the system physically move illegal drugs under the border.
Agents found more than eight tons of marijuana and 325 pounds of cocaine inside the tunnel, according to ICE. The drugs have an estimated street value of $6.5 million.
Officials said this is the first time they’ve seen cocaine attempt to be smuggled through tunnels.
The tunnel, though recently completed, was not yet operational.