A spokesperson for U.S. Immigration and Customs Enforcement called it the most sophisticated passageway they've found in at least five years, perhaps ever.
Authorities said the 600-yard passage was equipped with a hydraulic lift, electric rail cars, a wooden staircase and wood floors from one end to the other.
More than 32 tons of marijuana were discovered and several arrests were made.
Mexican soldiers found the entrance on the south side of the border at a Tijuana warehouse after the U.S. opening was discovered on Tuesday. The entrance to the tunnel in Tijuana is on the same block as a federal police office.
Authorities believe operations in the tunnel began recently.
This is the second time in as many weeks a tunnel opening has been found in a warehouse in Otay Mesa. More than 70 tunnels have been found on the border in the past three years.
The Associated Press contributed to this report.
