U.S. and Mexican authorities confiscated approximately 30 tons of marijuana on Wednesday. It is the largest seizure ever along the San Diego border, and one of the largest in the U.S.

Law enforcement officials made the discovery after a semi truck leaving a warehouse in Otay Mesa, Calif., caught the attention of authorities, who followed the truck 80 miles north to a border checkpoint.

"In that tractor trailer was 10 tons of marijuana," said John Morton, director of Immigration and Customs Enforcement.

A man and his wife inside the truck were arrested.

When authorities went back to the warehouse, located 300 yards from the Mexican border fence, they found an additional 20 tons of marijuana along with a large rectangular hole leading to an underground tunnel.

"Some of these packages were out in the open and just laying on the floor here," said ICE special agent Joe Garcia. "You have to be on your hands and knees to get in [the tunnel]. There's ventilation, a little bit of a primitive rail system in there and there's some lighting."

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