LAREDO, Tex. -- A way to expedite trusted truckers across the border, the Customs-Trade Partnership Against Terrorism (C-TPAT) program isn't going exactly as planned -- especially at U.S.'s southern border.

According to an Associated Press report, Customs officials are concerned that drug smugglers are purposefully targeting C-TPAT-approved trucking companies and their FAST drivers, who have undergone extensive security background checks.

C-TPAT cargo hauled by FAST drivers gets priority clearance (9 out of 10 loads aren't visually inspected) at the border and, depending on the crossing, a dedicated lane.

Not surprisingly, though, drug smugglers are the kinds of shippers that place the most value on such a program. Drugs have been repeatedly found in C-TPAT trailers -- mostly at the U.S.-Mexico border, but there have been some instances on the northern front as well.

Although Mexican carriers account for 6 percent of the participants in the program, they were involved in half of the 71 security violations in the last two years, reports AP.

Officials say that trucking companies that promote their C-TPAT credentials for business reasons are most attractive to smugglers.

In August, U.S. Customs and Border Protection (CBP) issued a security bulletin, warning all C-TPAT members to be more vigilant in reviewing their security systems.

A handful of C-TPAT companies have failed to follow established security procedures, and lack corporate oversight.