The Mexican government says troops have discovered another drug-smuggling tunnel beneath the U.S.- Mexico border and seized more than 40 tons of marijuana.

The tunnel, beneath the Tijuana (Mexico) – San Diego (California) border was the fourth such discovery in the past week.

Authorities say three of the tunnels were still under construction, including a 365-meter passage that began in a Tijuana warehouse where the marijuana was seized, and extended 100 meters into the U.S. side.

The U.S. Drug Enforcement Administration says another site, the San Luis passageway, is the only known completed and fully-operational smuggling tunnel ever discovered in the Yuma, Arizona area.