Border officials nab record 15 tons of marijuana at San Diego border crossing
A marijuana plant (AFP Photo/Leon Neal)

LOS ANGELES (Reuters) - U.S. customs officers at a California border crossing seized more than 15 tons of marijuana hidden inside a tractor-trailer shipment designated as a cargo of mattresses, the biggest narcotics bust ever at that port of entry, officials said on Friday.

Plastic-wrapped packages of marijuana, with a street value estimated at nearly $19 million, were found stacked floor to ceiling inside a trailer at the Otay Mesa cargo port in San Diego on Thursday, according to the U.S. Customs and Border Protection agency.

The tractor-trailer came under suspicion when an X-ray examination of the cargo detected an "anomaly," leading customs and border officers to conduct a closer inspection of the vehicle.

The shipment of pot, wrapped in nearly 1,300 packages weighing 31,598 pounds, was immediately spotted by officers who opened the trailer door. The only signs of bedding were a few mattresses stacked along the wall at the opposite end of the trailer from the doors, officials said.

The truck driver, a 46-year-old Mexican citizen with a valid border-crossing card, was turned over to U.S. immigration agents.

The confiscated marijuana marked the greatest amount of illegal drugs ever seized at Otay Mesa, one of three ports of entry in the San Diego-Tijuana border area, and the second largest such seizure anywhere in the United States, according to Customs and Border Protection.

The only one bigger was a seizure of 35,265 pounds of marijuana confiscated at California's Calexico East port of entry, across the border from Mexicali, Mexico, in 2013, the agency said in a statement.

(Reporting by Steve Gorman; Editing by Ken Wills)