U.S. Customs and Border Protection discovered a total of 1,619 pounds of marijuana hidden inside cement stones at the Otay Mesa cargo port of entry Saturday in San Diego County.

The flatbed semi-truck manifest declared “red stone” as the truck underwent an initial inspection. An x-ray examination was recommended before a drug canine sniffed the trailer and alerted officers. Border Patrol discovered 577 large bags of what the CBP referred to as a “leafy green substance” inside of the fake boulders.

“My officers not only need to enforce typical import and export laws, but need to be vigilant for smuggling attempts like this,” explained Otay Mesa Cargo Port Director Rosa Hernandez. “Officers used their skills and tools at their disposal to find and seize the large shipment..”

Border Patrol accessed the hollow cement stones using sledgehammers and jackhammers and the tractor, trailer, and over $810,000 in narcotics was seized by law enforcement.

The bust adds to the outlandish amount of marijuana that has been confiscated while attempting to cross the border from Tijuana, Baja California in the last couple of years. In April, a freightliner carrying 7 tons of marijuana inside a trailer was caught attempting to cross. Last year more than 15 tons of cannabis was discovered hidden inside mattresses and cushions.