SAN DIEGO (AP) — Agents at a Southern California border crossing have seized nearly 16 tons of marijuana hidden in a truck that supposedly was hauling mattresses.

The Border Patrol says the pot was found at San Diego’s Otay Mesa crossing with Mexico on Thursday evening.

Authorities say the truck’s trailer was stacked floor to ceiling with plastic-wrapped bundles of pot, which had an estimated street value of about $19 million.

The Mexican driver was taken into custody.

Authorities say it’s the second-largest drug seizure ever made at a port of entry. The largest — more than 17 ½ tons of pot — was seized two years ago at the Mexican border crossing in Calexico.