US Customs and Border Protection (CBP) officers stopped a 48-year-old driver at the port on Monday evening, and after conducting a "non-intrusive" search, they discovered more than 3.5 million fentanyl pills valued at $21.1 million hidden among the produce.
The search was prompted when officers noticed "irregularities" with the tractor-trailer, prompting them to call in a narcotic detector dog who alerted them to the pills inside.
The driver, who has yet to be identified, has been taken into the custody of Immigration and Customs Enforcement for allegations of attempted narcotic smuggling.
"CBP recognizes our officers’ exceptional performance and applaud their continued efforts to protect and serve our communities," said Rosa Hernandez, port director for the Otay Mesa Cargo Facility.
"This seizure provides insight and displays how our officers work together in collaboration to keep this dangerous drug off the streets."
Drug smuggling through the border continues to be an issue, with 471 fentanyl seizures reported between October and March.
CBP has also conducted more than 4,200 meth and 1,200 cocaine seizures during that period.