Most of the heroin smuggled into the United States is brought overland across the SWB (mostly Mexican heroin and some SA heroin) with lesser amounts transported by couriers on commercial airlines (SA, SWA, and SEA heroin). Heroin is commonly transported commingled with other drugs, particularly methamphetamine. Seizures at the SWB declined in FY 2016 for the first time in almost a decade, despite increasing heroin production levels in Mexico. According to CBP, most heroin smuggled across the border is transported in small, multi- kilogram loads, in privately-owned vehicles, usually through California.
In CY 2016, 40 percent of the heroin seizures at the Southwest Border (1,695 kilograms) occurred in the San Diego Corridor (683 kilograms). This was a decrease from CY 2015, when 2,205 kilograms were seized at the border, with 1,136 kilograms seized in the San Diego Corridor. Seizures in the Tucson (429 kilograms) and Rio Grande Valley (258 kilograms) corridors were also significant in CY 2016 (see Figure 44).